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The vision of the New Zealand Primary Health Care Strategy (PHCS) is that people are part of local primary health care services that improve their health, keep them well, are easy to get to and co-ordinate their ongoing care and that primary health care services focus on better health for a population, and actively work to reduce health inequalities between different groups .1 A key element of the implementation of the PHCS was the formation of Primary Health Organisations (PHOs) and population enrolment in PHOs. Along with the benefit of a nominated primary healthcare team to co-ordinate a range of health services including opportunistic and/or proactive preventive care, the advantages of PHO enrolment include lower co-payment for primary care visits.2 Ideally, all eligible New Zealand residents should be enrolled. However, 100% PHO enrolment is unlikely because PHO enrolment is voluntary,2 and some people who are not enrolled may be well, and not perceive themselves to have any immediate health needs. These people may not see any advantage in PHO enrolment.PHO enrolment is considered an important indicator of access to primary health care services, and is a mandated indicator in DHB Maaori* health plans.3 This paper explores the possible explanations that may account for the long-standing observation of low Maaori and Asian PHO enrolment and over 100% Pacific enrolment in New Zealand as reported in many published documents.4-7 Furthermore, it considers how efforts to improve PHO enrolment, to facilitate access to primary health care services, might be better targeted by using available administrative health data sets.Standard calculation of PHO enrolment uses the Statistics New Zealand estimated resident population as a denominator.8 This paper describes an alternative method to calculate PHO enrolment by ethnicity using a Health Service Utilisation (HSU) population as a population denominator.Recent health service utilisation can be seen as a proxy of recent health services need, albeit an imperfect proxy. People who have had recent health service utilisation are more likely to benefit from PHO enrolment than people have not had recent health service utilisation. For example, if a primary care follow-up is required following a hospitalisation, being enrolled in a PHO may result in lower co-payment fees and gives the opportunity for that care to be integrated with ongoing care by the primary care team of the patients choice. Since the contact details of people who have recently used health services are routinely recorded, the use of the health service utilisation population can potentially enable the health sector to readily identify people who have utilised health services recently but are not yet enrolled in a PHO. Therefore, people who might be missing out on the benefits of PHO enrolment could be better targeted. Since only routine administrative data from the Ministry of Health have been used, the methods can be readily replicated by the Ministry of Health, District Health Boards, and Primary Health Organisations.The estimated resident population used as a denominator in the standard calculation of PHO enrolment is one of two common population outputs from Statistics New Zealand, namely the census usually resident population, and the estimated resident population. These two populations are often misunderstood by the health sector; they should not be used interchangeably. The differences between the two concepts and how they should be used are discussed in the appendix.MethodsIn Aotearoa New Zealand, virtually all healthcare users are assigned a unique alphanumeric code, the National Health Index (NHI), at the time of their first contact with the health care system. The encrypted form of NHI was used in this study to ensure privacy and anonymity of individuals. As all datasets were entirely based on anonymous non-identifiable administrative data, and this work was carried out under the function of DHBs to assess and monitor the needs of their population for services,9 no formal ethical review from the Health and Disability Ethics Committee was required, as per New Zealand ethical guidelines.10The following datasets were sourced from the Ministry of Health. National Minimum Dataset (inpatient hospital events; NMDS, New Zealand coverage) National Non-admitted Patient Collection (outpatients, ED and community visits; NNPAC, New Zealand coverage) Pharmaceutical Collection (PHARMHOUSE, Northern region coverage only) Laboratory Claims Collection (Northern Region coverage only) Primary Health Organisation (PHO) Enrolment Collection, (New Zealand coverage) General Medical Subsidy Data Mart (New Zealand coverage) National Mortality Collection (New Zealand coverage) Master encrypted and secondary encrypted NHI look up list All the unique encrypted NHIs recorded in 2013 from any of the above datasets were merged to form a Health Service Utilisation (HSU) population. The latest domicile code for an individual as recorded in any of the datasets was used to determine the DHB of domicile. The master encrypted and secondary encrypted NHI look-up list was used to ensure any known duplicated encrypted NHIs were not double counted. Effectively, the HSU population includes virtually everyone living in the area covered by the datasets (in this case limited to the Northern region because not all datasets had national coverage) who had a publicly-funded health service contact or was enrolled in PHO in 2013.The HSU population is the inclusion criteria of this study. Ethnicity for the HSU population is derived from the NHI used to link the datasets and in keeping with the New Zealand health sector standard,11 ethnicity was prioritised from multiple ethnic codes in the following order: Maaori, Pacific peoples, Asian, New Zealand European/Other.Aggregated estimated resident population numbers and population projections (MOH version 2013 based on New Zealand Census 2006) were sourced from Statistics New Zealand. This estimated resident population denominator was provided by Statistics New Zealand for the Ministry of Health in November 2013 which was based on projections from the 2006 Census.1. Standard method of calculating the percentage of people enrolled in a Primary Health OrganisationCalculating PHO enrolment rate using the standard method typically involves using the number of people enrolled in an area of interest divided by the corresponding estimated resident population in the same time period of interest. The numerator and denominator are not individually linked.Definitions: Denominator: Estimated resident population from Statistics New Zealand in 2013 by age, gender, ethnicity and DHB. Numerator: The corresponding number of people enrolled by age, gender, ethnicity and DHB as per PHO enrolment 2013 Quarter Three. Quarter Three coincides with the annual June population estimate from Statistics NZ for the relevant year. 2. Alternative indicator: Percentage of people enrolled in a PHO within the CMDHB Health Service Utilisation population in 2013The denominator is the Health Service Utilisation (HSU) population in 2013 derived as described above from record linkage of Ministry of Health datasets via encrypted NHI. The HSU population for this study were defined as below: people who were domiciled in Counties Manukau in 2013, and enrolled in a PHO, or had a publicly-funded health service contact in 2013, namely inpatient and outpatient services, pharmaceutical dispensing, community laboratory test, GMS claims, and were still alive at 31 December 2013. The numerator is the number of people who were enrolled in a PHO (anywhere in New Zealand) at some point during 2013, as determined by record linkage at encrypted NHI level within the HSU population. The HSU population is the inclusion criteria of the study population and the PHO enrolment status is determined for each individual within the HSU population via encrypted NHI linkage between the PHO enrolment data and HSU population. Since the numerator and denominator are individually linked, the ethnicity and demographic variables in the study were identical for an individual, based on the NHI used for linkage, so the numerator-denominator mismatch described in previous reports is eliminated.12 Note that ethnicity in the PHO register may differ from the ethnicity recorded in the NHI, and this study uses the NHI ethnicity for an individual to avoid numerator denominator mismatch.Six quarters of PHO enrolment (2013 Q1\u20134, 2014 Q1\u20132) were used to determine the enrolment status in 2013, based on the starting date of enrolment, because some of the 2013 enrolment statuses were subsequently recorded late, in the 2014 PHO enrolment datasets.3. Subgroup analysis:a. The percentage of people discharged from either of the two key inpatient facilities for CMDHB: Middlemore Hospital (MMH) and Manukau Surgical Centre (MSC) in 2012 and 2013 who were not enrolled within one month of discharge.Definitions: Denominator: Number of people who were discharged from CMDHB hospital facilities in 2012 and 2013 (casemix acute, arranged and elective discharges). People who died within one month of discharge were excluded. Note: One individual may be discharged more than once in a year. Numerator: The number of people discharged from MMH and/or MSC who were not enrolled (anywhere in New Zealand) based on the date of enrolment in 2012 and 2013 as recorded in the PHO enrolment data within a month of hospital discharge. Four quarters of PHO enrolment data in the relevant year and the first two quarters of PHO enrolment data in the subsequent year were examined. The start date of enrolment as recorded in the PHO enrolment record was used. The latest/end date of enrolment determines the latest quarter that an individual is present in the PHO data. The cut off dates for financial claims were used; eg, if an individual is last present in Q1 then it is assumed the person is enrolled on 20 November in the previous year, Q2: 20 February in the year of interest, Q3: 20 May, Q4: 20 August. b. A simplified annual method of estimating the percentage of enrolment can be carried out by determining whether people discharged (excluding deaths) in 2013 were enrolled in the 2014 Q2 PHO enrolment, or not.Definitions: Denominator: Number of people with CMDHB hospital casemix discharges in 2013 excluding death. Numerator: Out of people who were discharged from CMDHB hospital facilities in 2013, the number of people who enrolled in 2014 Q2 nationally (Cut-off date: 20 February). ResultsStandard method of calculating PHO enrolment:Comparing the population estimates released from Statistics New Zealand with the PHO enrolment data at a high level suggests PHO enrolment for the CMDHB population had a coverage of 97% in a snapshot view at Quarter Three that coincides with the annual June population estimate, 2013. The estimated percentage of PHO enrolment is the number of people enrolled, divided by estimated resident population from Statistics New Zealand in CMDHB in the corresponding age group in 2013.Females of child-bearing age appear to have a relatively high level of enrolment (Table 1). Males between the ages of 15 to 29 appear to have a lower level of enrolment. In the older age groups, there are more people enrolled than the Statistics New Zealand population estimates.Table 1: Estimated PHO enrolment rate for the CMDHB population in 2013 by age by the standard method Age (years) Number of people enrolled as per 2013 Q3 PHO enrolment register Estimated Resident Population from Stats NZ in 2013 Estimated PHO enrolment rate (standard method) Females Males Females Males Females Males 0-4 20,183 21,339 20,460 21,440 99% 100% 5-9 20,439 21,727 20,060 21,060 102% 103% 10-14 18,971 19,975 19,460 20,430 97% 98% 15-19 18,918 19,066 19,660 20,270 96% 94% 20-24 19,135 18,048 19,800 20,960 97% 86% 25-29 17,987 15,447 18,230 18,020 99% 86% 30-34 17,538 14,719 17,540 15,510 100% 95% 35-39 17,058 14,533 16,990 14,730 100% 99% 40-44 18,796 16,621 19,220 16,730 98% 99% 45-49 17,830 16,863 18,340 17,090 97% 99% 50-54 16,576 15,618 17,170 16,050 97% 97% 55-59 13,603 13,001 13,940 13,480 98% 96% 60-64 11,571 11,076 11,810 11,180 98% 99% 65-69 9,466 9,061 10,010 9,390 95% 96% 70-74 6,965 6,461 7,190 6,610 97% 98% 75-79 4,826 4,209 4,930 4,170 98% 101% 80-84 3,573 2,673 3,500 2,690 102% 99% 85-89 2,180 1,404 2,030 1,260 107% 111% >90 1,228 492 1,200 500 102% 98% Overall 256,843 242,333 261,540 251,570 98% 96% When enrolment is compared across ethnic groups, Maaori PHO enrolment appears to be much lower that might be expected when compared to estimated resident population from Statistics New Zealand (89% enrolment in Quarter Three 2013) (Table 2). On the other hand, Pacific PHO enrolment is much higher than the number expected based on the corresponding estimated resident population (111% enrolment in CMDHB). This pattern of PHO enrolment for CMDHB is generally consistent with the overall New Zealand pattern for people of these ethnicities (Table 2) and, as discussed subsequently, needs to be considered in the light of likely dataset mismatch in relation to identified ethnicity.Table 2: PHO enrolment rate by District Health Board in New Zealand and ethnicity in Quarter 3 2013, using the standard method DHB Maaori Pacific Asian NZ European & others Overall Auckland 79% 115% 71% 102% 93% Bay of Plenty 93% 93% 93% 99% 97% Canterbury 80% 96% 74% 99% 95% Capital and Coast 86% 99% 79% 96% 93% Counties Manukau 89% 111% 77% 105% 97% Hawkes Bay 92% 96% 90% 99% 97% Hutt 85% 94% 98% 100% 97% Lakes 100% 90% 73% 102% 100% MidCentral 85% 94% 76% 96% 93% Nelson Marlborough 87% 93% 97% 99% 98% Northland 104% 83% 93% 102% 102% South Canterbury 77% 104% 115% 101% 99% Southern 79% 99% 68% 95% 92% Tairawhiti 100% 93% 81% 98% 98% Taranaki 87% 84% 76% 100% 97% Waikato 94% 100% 75% 100% 97% Wairarapa 103% 105% 96% 103% 103% Waitemata 79% 100% 76% 101% 94% West Coast 91% 102% 115% 96% 96% Whanganui 87% 108% 73% 100% 96% Overall New Zealand 89% 106% 76% 100% 96% Alternative indicator: Percentage of people enrolled within the CMDHB Health Service Utilisation population in 2013In CMDHB, out of the people who had contact with publicly-funded health services in 2013, 98% were enrolled at some point in 2013 (Table 3). In other words, only 2% of the Counties Manukau population who had used publicly-funded health services were not enrolled. In contrast to the standard method, the percentage of enrolment was similar across all the selected ethnicities (Table 3). Overall, females had a marginally higher PHO enrolment than males. Pacific people had a marginally lower enrolment rate than Maaori.Table 3: Percentage of PHO enrolment within the CMDHB Health Service Utilisation population in 2013 by ethnicity Ethnicity Enrolled Not enrolled Number of people in the CMDHB health service utilisation population Percentage of enrolment Maaori 85,436 1,457 86,893 98.3% Pacific 130,985 3,150 134,135 97.7% Asian 97,302 2,357 99,659 97.6% NZ European & Others 198,228 3,472 201,700 98.3% Overall 511,951 10,436 522,387 98.0% Using the HSU population as a denominator, children aged 0\u20134 years had one of the lowest rates of PHO enrolment (Table 4).Table 4: Percentage of PHO enrolment within the CMDHB Health Service Utilisation population by summarised age groups and gender Age (years) Females Males Enrolled Not enrolled Number of people in the CM HSU population % of enrolmt Enrolled Not enrolled Number of people in the CM HSU population % of enrolmt 00-04 20,979 719 21,698 96.7% 22,361 802 23,163 96.5% 05-14 40,434 592 41,026 98.6% 42,575 665 43,240 98.5% 15-24 39,170 910 40,080 97.7% 37,887 1,141 39,028 97.1% 25-44 72,848 1,255 74,103 98.3% 62,503 1,921 64,424 97.0% 45-64 61,281 785 62,066 98.7% 57,821 1,025 58,846 98.3% 65 & over 29,027 334 29,361 98.9% 25,065 287 25,352 98.9% Overall 263,739 4,595 268,334 98.3% 248,212 5,841 254,053 97.7% The PHO enrolment rate was similar across the four ethnicities using the HSU population as a denominator (Table 5).Table 5: Percentage of PHO enrolment within the CMDHB Health Service Utilisation population by age and ethnicity Age (Years) Maaori Pacific Asian NZ European and others \

Summary

Abstract

Aim

Estimating Primary Health Organisation (PHO) enrolment rates with a Census-derived estimated resident population denominator may provide misleading results because of numerator and denominator mismatch. This study uses the Health Service Utilisation (HSU) population denominator as an alternative.

Method

A HSU population was generated by record linkage of routinely collected datasets from the Ministry of Health via encrypted National Health Index (NHI). We compare PHO enrolment rates by age and ethnicity in Counties Manukau District Health Board (CMDHB) in 2013.

Results

In CMDHB, 98% of people who had utilised publicly-funded health services in 2013 were enrolled in a PHO in 2013. Using the HSU population as a denominator, PHO enrolment rates for Maaori, Pacific, Asian, New Zealand European/Other population groups were 98.3%, 97.7%, 97.6%, and 98.3% respectively. Just under 4% of people discharged from CMDHB inpatient facilities were not enrolled in a PHO within a month from the day of discharge in 2013.

Conclusion

Using the HSU population as a proxy of health services need, PHO enrolment rates were similar across ethnicities in the CMDHB population. Support to improve PHO enrolment coverage would be more efficient if the HSU population were used to target people who are not yet enrolled in a PHO.

Author Information

Wing Cheuk Chan, Public health Physician, Population Health, Counties Manukau District Health Board, South Auckland; Dean Papaconstantinou, Health Analyst, Population Health, Counties Manukau District Health Board, South Auckland; Doone Winnard, Clinical Director, Population Health, Counties Manukau District Health Board, South Auckland.

Acknowledgements

'- Funding: This study was undertaken as a result of work undertaken in the population health team for Counties Manukau District Health Board (CMDHB). -

Correspondence

Wing Cheuk Chan, Counties Manukau District Health Board

Correspondence Email

wingcheuk.chan@cmdhb.org.nz

Competing Interests

All authors were paid employees of CMDHB.

'- - Ministry of Health. The Primary Health Care Strategy. Wellington: Ministry of Health; 2001. Ministry of Health. Enrolling with a Primary Health Organisation. Wellington: Ministry of Health; 2002. Ministry of Health. 2015/16 Maaori Health Plan Template Guidelines. Wellington: Ministry of Health; 2015. Counties Manukau Health. Counties Manukau District Health Board Maaori Health Plan 2014/15: Manukau 2014. Waitemata District Health Broad. Waitemata DHB annual report for the year ended 30 June 2005. Auckland: Waitemata District Health Broad; 2005. Malcolm L. Towards a reliable and accurate ethnicity database at district and national levels: progress in Canterbury. N Z Med J 2010;123:43-8. Mehta S. Health needs assessment of Asian people living in the Auckland region. Auckland: Northern DHB Support Agency; 2012. Statistics New Zealand. Evaluation of administrative data sources for subnational population estimates. Wellington: Statistics New Zealand; 2013. New Zealand Government. New Zealand Public Health and Disability Act 2000. Wellington: New Zealand Government; 2000. National Ethics Advisory Committee. Ethical Guidelines for Observational Studies: Observational research, audits and related activities: Revised edition. Wellington: Ministry of Health; 2012. Ministry of Health. Ethnicity Data Protocols for the Health and Disability Sector. Wellington: Ministry of Health; 2004. Ajwani S, Blakely T, Robson B, Tobias M, M. B. Decades of Disparity: Ethnic mortality trends in New Zealand 1980-1999. Wellington: Ministry of Health and University of Otago; 2003. Statistics New Zealand. Understanding substitution and imputation in the 2013 Census. Wellington: Statistics New Zealand; 2014. Capitation rates from 1 July 2014. Ministry of Health, 2014. (Accessed 21/11/2014, at http://www.health.govt.nz/our-work/primary-health-care/primary-health-care-subsidies-and-services/capitation-rates.) Statistics New Zealand. Understanding and Working with Ethnicity Data. Wellington: Statistics New Zealand; 2005. Burton J, Nandi A, Platt L. Measuring ethnicity: challenges and opportunities for survey research. Ethnic and Racial Studies 2010;33:1332-49. Statistics New Zealand. Coverage in the 2013 Census based on the New Zealand 2013 Post-enumeration Survey. Wellington: Statistics New Zealand; 2014. 2013 Census information by variable: ethnicity. Statistics New Zealand, 2013. (Accessed 21/11/2014, at http://www.stats.govt.nz/Census/2013-census/info-about-2013-census-data/information-by-variable/ethnicity.aspx.) Chan WC, Jackson G, Wright CS, et al. The future of population registers: linking routine health datasets to assess a populations current glycaemic status for quality improvement. BMJ Open 2014;4:e003975. Minister of Health. Newborn Pre Enrolment Toolkit. Wellington: Ministry of Health; 2012. Statistics New Zealand. Estimated resident population 2013: Data sources and methods. Wellington: Statistics New Zealand; 2014. Statistics New Zealand. A Report on the 2006 Post-enumeration Survey. Wellington: Statistics New Zealand; 2007.- -

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The vision of the New Zealand Primary Health Care Strategy (PHCS) is that people are part of local primary health care services that improve their health, keep them well, are easy to get to and co-ordinate their ongoing care and that primary health care services focus on better health for a population, and actively work to reduce health inequalities between different groups .1 A key element of the implementation of the PHCS was the formation of Primary Health Organisations (PHOs) and population enrolment in PHOs. Along with the benefit of a nominated primary healthcare team to co-ordinate a range of health services including opportunistic and/or proactive preventive care, the advantages of PHO enrolment include lower co-payment for primary care visits.2 Ideally, all eligible New Zealand residents should be enrolled. However, 100% PHO enrolment is unlikely because PHO enrolment is voluntary,2 and some people who are not enrolled may be well, and not perceive themselves to have any immediate health needs. These people may not see any advantage in PHO enrolment.PHO enrolment is considered an important indicator of access to primary health care services, and is a mandated indicator in DHB Maaori* health plans.3 This paper explores the possible explanations that may account for the long-standing observation of low Maaori and Asian PHO enrolment and over 100% Pacific enrolment in New Zealand as reported in many published documents.4-7 Furthermore, it considers how efforts to improve PHO enrolment, to facilitate access to primary health care services, might be better targeted by using available administrative health data sets.Standard calculation of PHO enrolment uses the Statistics New Zealand estimated resident population as a denominator.8 This paper describes an alternative method to calculate PHO enrolment by ethnicity using a Health Service Utilisation (HSU) population as a population denominator.Recent health service utilisation can be seen as a proxy of recent health services need, albeit an imperfect proxy. People who have had recent health service utilisation are more likely to benefit from PHO enrolment than people have not had recent health service utilisation. For example, if a primary care follow-up is required following a hospitalisation, being enrolled in a PHO may result in lower co-payment fees and gives the opportunity for that care to be integrated with ongoing care by the primary care team of the patients choice. Since the contact details of people who have recently used health services are routinely recorded, the use of the health service utilisation population can potentially enable the health sector to readily identify people who have utilised health services recently but are not yet enrolled in a PHO. Therefore, people who might be missing out on the benefits of PHO enrolment could be better targeted. Since only routine administrative data from the Ministry of Health have been used, the methods can be readily replicated by the Ministry of Health, District Health Boards, and Primary Health Organisations.The estimated resident population used as a denominator in the standard calculation of PHO enrolment is one of two common population outputs from Statistics New Zealand, namely the census usually resident population, and the estimated resident population. These two populations are often misunderstood by the health sector; they should not be used interchangeably. The differences between the two concepts and how they should be used are discussed in the appendix.MethodsIn Aotearoa New Zealand, virtually all healthcare users are assigned a unique alphanumeric code, the National Health Index (NHI), at the time of their first contact with the health care system. The encrypted form of NHI was used in this study to ensure privacy and anonymity of individuals. As all datasets were entirely based on anonymous non-identifiable administrative data, and this work was carried out under the function of DHBs to assess and monitor the needs of their population for services,9 no formal ethical review from the Health and Disability Ethics Committee was required, as per New Zealand ethical guidelines.10The following datasets were sourced from the Ministry of Health. National Minimum Dataset (inpatient hospital events; NMDS, New Zealand coverage) National Non-admitted Patient Collection (outpatients, ED and community visits; NNPAC, New Zealand coverage) Pharmaceutical Collection (PHARMHOUSE, Northern region coverage only) Laboratory Claims Collection (Northern Region coverage only) Primary Health Organisation (PHO) Enrolment Collection, (New Zealand coverage) General Medical Subsidy Data Mart (New Zealand coverage) National Mortality Collection (New Zealand coverage) Master encrypted and secondary encrypted NHI look up list All the unique encrypted NHIs recorded in 2013 from any of the above datasets were merged to form a Health Service Utilisation (HSU) population. The latest domicile code for an individual as recorded in any of the datasets was used to determine the DHB of domicile. The master encrypted and secondary encrypted NHI look-up list was used to ensure any known duplicated encrypted NHIs were not double counted. Effectively, the HSU population includes virtually everyone living in the area covered by the datasets (in this case limited to the Northern region because not all datasets had national coverage) who had a publicly-funded health service contact or was enrolled in PHO in 2013.The HSU population is the inclusion criteria of this study. Ethnicity for the HSU population is derived from the NHI used to link the datasets and in keeping with the New Zealand health sector standard,11 ethnicity was prioritised from multiple ethnic codes in the following order: Maaori, Pacific peoples, Asian, New Zealand European/Other.Aggregated estimated resident population numbers and population projections (MOH version 2013 based on New Zealand Census 2006) were sourced from Statistics New Zealand. This estimated resident population denominator was provided by Statistics New Zealand for the Ministry of Health in November 2013 which was based on projections from the 2006 Census.1. Standard method of calculating the percentage of people enrolled in a Primary Health OrganisationCalculating PHO enrolment rate using the standard method typically involves using the number of people enrolled in an area of interest divided by the corresponding estimated resident population in the same time period of interest. The numerator and denominator are not individually linked.Definitions: Denominator: Estimated resident population from Statistics New Zealand in 2013 by age, gender, ethnicity and DHB. Numerator: The corresponding number of people enrolled by age, gender, ethnicity and DHB as per PHO enrolment 2013 Quarter Three. Quarter Three coincides with the annual June population estimate from Statistics NZ for the relevant year. 2. Alternative indicator: Percentage of people enrolled in a PHO within the CMDHB Health Service Utilisation population in 2013The denominator is the Health Service Utilisation (HSU) population in 2013 derived as described above from record linkage of Ministry of Health datasets via encrypted NHI. The HSU population for this study were defined as below: people who were domiciled in Counties Manukau in 2013, and enrolled in a PHO, or had a publicly-funded health service contact in 2013, namely inpatient and outpatient services, pharmaceutical dispensing, community laboratory test, GMS claims, and were still alive at 31 December 2013. The numerator is the number of people who were enrolled in a PHO (anywhere in New Zealand) at some point during 2013, as determined by record linkage at encrypted NHI level within the HSU population. The HSU population is the inclusion criteria of the study population and the PHO enrolment status is determined for each individual within the HSU population via encrypted NHI linkage between the PHO enrolment data and HSU population. Since the numerator and denominator are individually linked, the ethnicity and demographic variables in the study were identical for an individual, based on the NHI used for linkage, so the numerator-denominator mismatch described in previous reports is eliminated.12 Note that ethnicity in the PHO register may differ from the ethnicity recorded in the NHI, and this study uses the NHI ethnicity for an individual to avoid numerator denominator mismatch.Six quarters of PHO enrolment (2013 Q1\u20134, 2014 Q1\u20132) were used to determine the enrolment status in 2013, based on the starting date of enrolment, because some of the 2013 enrolment statuses were subsequently recorded late, in the 2014 PHO enrolment datasets.3. Subgroup analysis:a. The percentage of people discharged from either of the two key inpatient facilities for CMDHB: Middlemore Hospital (MMH) and Manukau Surgical Centre (MSC) in 2012 and 2013 who were not enrolled within one month of discharge.Definitions: Denominator: Number of people who were discharged from CMDHB hospital facilities in 2012 and 2013 (casemix acute, arranged and elective discharges). People who died within one month of discharge were excluded. Note: One individual may be discharged more than once in a year. Numerator: The number of people discharged from MMH and/or MSC who were not enrolled (anywhere in New Zealand) based on the date of enrolment in 2012 and 2013 as recorded in the PHO enrolment data within a month of hospital discharge. Four quarters of PHO enrolment data in the relevant year and the first two quarters of PHO enrolment data in the subsequent year were examined. The start date of enrolment as recorded in the PHO enrolment record was used. The latest/end date of enrolment determines the latest quarter that an individual is present in the PHO data. The cut off dates for financial claims were used; eg, if an individual is last present in Q1 then it is assumed the person is enrolled on 20 November in the previous year, Q2: 20 February in the year of interest, Q3: 20 May, Q4: 20 August. b. A simplified annual method of estimating the percentage of enrolment can be carried out by determining whether people discharged (excluding deaths) in 2013 were enrolled in the 2014 Q2 PHO enrolment, or not.Definitions: Denominator: Number of people with CMDHB hospital casemix discharges in 2013 excluding death. Numerator: Out of people who were discharged from CMDHB hospital facilities in 2013, the number of people who enrolled in 2014 Q2 nationally (Cut-off date: 20 February). ResultsStandard method of calculating PHO enrolment:Comparing the population estimates released from Statistics New Zealand with the PHO enrolment data at a high level suggests PHO enrolment for the CMDHB population had a coverage of 97% in a snapshot view at Quarter Three that coincides with the annual June population estimate, 2013. The estimated percentage of PHO enrolment is the number of people enrolled, divided by estimated resident population from Statistics New Zealand in CMDHB in the corresponding age group in 2013.Females of child-bearing age appear to have a relatively high level of enrolment (Table 1). Males between the ages of 15 to 29 appear to have a lower level of enrolment. In the older age groups, there are more people enrolled than the Statistics New Zealand population estimates.Table 1: Estimated PHO enrolment rate for the CMDHB population in 2013 by age by the standard method Age (years) Number of people enrolled as per 2013 Q3 PHO enrolment register Estimated Resident Population from Stats NZ in 2013 Estimated PHO enrolment rate (standard method) Females Males Females Males Females Males 0-4 20,183 21,339 20,460 21,440 99% 100% 5-9 20,439 21,727 20,060 21,060 102% 103% 10-14 18,971 19,975 19,460 20,430 97% 98% 15-19 18,918 19,066 19,660 20,270 96% 94% 20-24 19,135 18,048 19,800 20,960 97% 86% 25-29 17,987 15,447 18,230 18,020 99% 86% 30-34 17,538 14,719 17,540 15,510 100% 95% 35-39 17,058 14,533 16,990 14,730 100% 99% 40-44 18,796 16,621 19,220 16,730 98% 99% 45-49 17,830 16,863 18,340 17,090 97% 99% 50-54 16,576 15,618 17,170 16,050 97% 97% 55-59 13,603 13,001 13,940 13,480 98% 96% 60-64 11,571 11,076 11,810 11,180 98% 99% 65-69 9,466 9,061 10,010 9,390 95% 96% 70-74 6,965 6,461 7,190 6,610 97% 98% 75-79 4,826 4,209 4,930 4,170 98% 101% 80-84 3,573 2,673 3,500 2,690 102% 99% 85-89 2,180 1,404 2,030 1,260 107% 111% >90 1,228 492 1,200 500 102% 98% Overall 256,843 242,333 261,540 251,570 98% 96% When enrolment is compared across ethnic groups, Maaori PHO enrolment appears to be much lower that might be expected when compared to estimated resident population from Statistics New Zealand (89% enrolment in Quarter Three 2013) (Table 2). On the other hand, Pacific PHO enrolment is much higher than the number expected based on the corresponding estimated resident population (111% enrolment in CMDHB). This pattern of PHO enrolment for CMDHB is generally consistent with the overall New Zealand pattern for people of these ethnicities (Table 2) and, as discussed subsequently, needs to be considered in the light of likely dataset mismatch in relation to identified ethnicity.Table 2: PHO enrolment rate by District Health Board in New Zealand and ethnicity in Quarter 3 2013, using the standard method DHB Maaori Pacific Asian NZ European & others Overall Auckland 79% 115% 71% 102% 93% Bay of Plenty 93% 93% 93% 99% 97% Canterbury 80% 96% 74% 99% 95% Capital and Coast 86% 99% 79% 96% 93% Counties Manukau 89% 111% 77% 105% 97% Hawkes Bay 92% 96% 90% 99% 97% Hutt 85% 94% 98% 100% 97% Lakes 100% 90% 73% 102% 100% MidCentral 85% 94% 76% 96% 93% Nelson Marlborough 87% 93% 97% 99% 98% Northland 104% 83% 93% 102% 102% South Canterbury 77% 104% 115% 101% 99% Southern 79% 99% 68% 95% 92% Tairawhiti 100% 93% 81% 98% 98% Taranaki 87% 84% 76% 100% 97% Waikato 94% 100% 75% 100% 97% Wairarapa 103% 105% 96% 103% 103% Waitemata 79% 100% 76% 101% 94% West Coast 91% 102% 115% 96% 96% Whanganui 87% 108% 73% 100% 96% Overall New Zealand 89% 106% 76% 100% 96% Alternative indicator: Percentage of people enrolled within the CMDHB Health Service Utilisation population in 2013In CMDHB, out of the people who had contact with publicly-funded health services in 2013, 98% were enrolled at some point in 2013 (Table 3). In other words, only 2% of the Counties Manukau population who had used publicly-funded health services were not enrolled. In contrast to the standard method, the percentage of enrolment was similar across all the selected ethnicities (Table 3). Overall, females had a marginally higher PHO enrolment than males. Pacific people had a marginally lower enrolment rate than Maaori.Table 3: Percentage of PHO enrolment within the CMDHB Health Service Utilisation population in 2013 by ethnicity Ethnicity Enrolled Not enrolled Number of people in the CMDHB health service utilisation population Percentage of enrolment Maaori 85,436 1,457 86,893 98.3% Pacific 130,985 3,150 134,135 97.7% Asian 97,302 2,357 99,659 97.6% NZ European & Others 198,228 3,472 201,700 98.3% Overall 511,951 10,436 522,387 98.0% Using the HSU population as a denominator, children aged 0\u20134 years had one of the lowest rates of PHO enrolment (Table 4).Table 4: Percentage of PHO enrolment within the CMDHB Health Service Utilisation population by summarised age groups and gender Age (years) Females Males Enrolled Not enrolled Number of people in the CM HSU population % of enrolmt Enrolled Not enrolled Number of people in the CM HSU population % of enrolmt 00-04 20,979 719 21,698 96.7% 22,361 802 23,163 96.5% 05-14 40,434 592 41,026 98.6% 42,575 665 43,240 98.5% 15-24 39,170 910 40,080 97.7% 37,887 1,141 39,028 97.1% 25-44 72,848 1,255 74,103 98.3% 62,503 1,921 64,424 97.0% 45-64 61,281 785 62,066 98.7% 57,821 1,025 58,846 98.3% 65 & over 29,027 334 29,361 98.9% 25,065 287 25,352 98.9% Overall 263,739 4,595 268,334 98.3% 248,212 5,841 254,053 97.7% The PHO enrolment rate was similar across the four ethnicities using the HSU population as a denominator (Table 5).Table 5: Percentage of PHO enrolment within the CMDHB Health Service Utilisation population by age and ethnicity Age (Years) Maaori Pacific Asian NZ European and others \

Summary

Abstract

Aim

Estimating Primary Health Organisation (PHO) enrolment rates with a Census-derived estimated resident population denominator may provide misleading results because of numerator and denominator mismatch. This study uses the Health Service Utilisation (HSU) population denominator as an alternative.

Method

A HSU population was generated by record linkage of routinely collected datasets from the Ministry of Health via encrypted National Health Index (NHI). We compare PHO enrolment rates by age and ethnicity in Counties Manukau District Health Board (CMDHB) in 2013.

Results

In CMDHB, 98% of people who had utilised publicly-funded health services in 2013 were enrolled in a PHO in 2013. Using the HSU population as a denominator, PHO enrolment rates for Maaori, Pacific, Asian, New Zealand European/Other population groups were 98.3%, 97.7%, 97.6%, and 98.3% respectively. Just under 4% of people discharged from CMDHB inpatient facilities were not enrolled in a PHO within a month from the day of discharge in 2013.

Conclusion

Using the HSU population as a proxy of health services need, PHO enrolment rates were similar across ethnicities in the CMDHB population. Support to improve PHO enrolment coverage would be more efficient if the HSU population were used to target people who are not yet enrolled in a PHO.

Author Information

Wing Cheuk Chan, Public health Physician, Population Health, Counties Manukau District Health Board, South Auckland; Dean Papaconstantinou, Health Analyst, Population Health, Counties Manukau District Health Board, South Auckland; Doone Winnard, Clinical Director, Population Health, Counties Manukau District Health Board, South Auckland.

Acknowledgements

'- Funding: This study was undertaken as a result of work undertaken in the population health team for Counties Manukau District Health Board (CMDHB). -

Correspondence

Wing Cheuk Chan, Counties Manukau District Health Board

Correspondence Email

wingcheuk.chan@cmdhb.org.nz

Competing Interests

All authors were paid employees of CMDHB.

'- - Ministry of Health. The Primary Health Care Strategy. Wellington: Ministry of Health; 2001. Ministry of Health. Enrolling with a Primary Health Organisation. Wellington: Ministry of Health; 2002. Ministry of Health. 2015/16 Maaori Health Plan Template Guidelines. Wellington: Ministry of Health; 2015. Counties Manukau Health. Counties Manukau District Health Board Maaori Health Plan 2014/15: Manukau 2014. Waitemata District Health Broad. Waitemata DHB annual report for the year ended 30 June 2005. Auckland: Waitemata District Health Broad; 2005. Malcolm L. Towards a reliable and accurate ethnicity database at district and national levels: progress in Canterbury. N Z Med J 2010;123:43-8. Mehta S. Health needs assessment of Asian people living in the Auckland region. Auckland: Northern DHB Support Agency; 2012. Statistics New Zealand. Evaluation of administrative data sources for subnational population estimates. Wellington: Statistics New Zealand; 2013. New Zealand Government. New Zealand Public Health and Disability Act 2000. Wellington: New Zealand Government; 2000. National Ethics Advisory Committee. Ethical Guidelines for Observational Studies: Observational research, audits and related activities: Revised edition. Wellington: Ministry of Health; 2012. Ministry of Health. Ethnicity Data Protocols for the Health and Disability Sector. Wellington: Ministry of Health; 2004. Ajwani S, Blakely T, Robson B, Tobias M, M. B. Decades of Disparity: Ethnic mortality trends in New Zealand 1980-1999. Wellington: Ministry of Health and University of Otago; 2003. Statistics New Zealand. Understanding substitution and imputation in the 2013 Census. Wellington: Statistics New Zealand; 2014. Capitation rates from 1 July 2014. Ministry of Health, 2014. (Accessed 21/11/2014, at http://www.health.govt.nz/our-work/primary-health-care/primary-health-care-subsidies-and-services/capitation-rates.) Statistics New Zealand. Understanding and Working with Ethnicity Data. Wellington: Statistics New Zealand; 2005. Burton J, Nandi A, Platt L. Measuring ethnicity: challenges and opportunities for survey research. Ethnic and Racial Studies 2010;33:1332-49. Statistics New Zealand. Coverage in the 2013 Census based on the New Zealand 2013 Post-enumeration Survey. Wellington: Statistics New Zealand; 2014. 2013 Census information by variable: ethnicity. Statistics New Zealand, 2013. (Accessed 21/11/2014, at http://www.stats.govt.nz/Census/2013-census/info-about-2013-census-data/information-by-variable/ethnicity.aspx.) Chan WC, Jackson G, Wright CS, et al. The future of population registers: linking routine health datasets to assess a populations current glycaemic status for quality improvement. BMJ Open 2014;4:e003975. Minister of Health. Newborn Pre Enrolment Toolkit. Wellington: Ministry of Health; 2012. Statistics New Zealand. Estimated resident population 2013: Data sources and methods. Wellington: Statistics New Zealand; 2014. Statistics New Zealand. A Report on the 2006 Post-enumeration Survey. Wellington: Statistics New Zealand; 2007.- -

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The vision of the New Zealand Primary Health Care Strategy (PHCS) is that people are part of local primary health care services that improve their health, keep them well, are easy to get to and co-ordinate their ongoing care and that primary health care services focus on better health for a population, and actively work to reduce health inequalities between different groups .1 A key element of the implementation of the PHCS was the formation of Primary Health Organisations (PHOs) and population enrolment in PHOs. Along with the benefit of a nominated primary healthcare team to co-ordinate a range of health services including opportunistic and/or proactive preventive care, the advantages of PHO enrolment include lower co-payment for primary care visits.2 Ideally, all eligible New Zealand residents should be enrolled. However, 100% PHO enrolment is unlikely because PHO enrolment is voluntary,2 and some people who are not enrolled may be well, and not perceive themselves to have any immediate health needs. These people may not see any advantage in PHO enrolment.PHO enrolment is considered an important indicator of access to primary health care services, and is a mandated indicator in DHB Maaori* health plans.3 This paper explores the possible explanations that may account for the long-standing observation of low Maaori and Asian PHO enrolment and over 100% Pacific enrolment in New Zealand as reported in many published documents.4-7 Furthermore, it considers how efforts to improve PHO enrolment, to facilitate access to primary health care services, might be better targeted by using available administrative health data sets.Standard calculation of PHO enrolment uses the Statistics New Zealand estimated resident population as a denominator.8 This paper describes an alternative method to calculate PHO enrolment by ethnicity using a Health Service Utilisation (HSU) population as a population denominator.Recent health service utilisation can be seen as a proxy of recent health services need, albeit an imperfect proxy. People who have had recent health service utilisation are more likely to benefit from PHO enrolment than people have not had recent health service utilisation. For example, if a primary care follow-up is required following a hospitalisation, being enrolled in a PHO may result in lower co-payment fees and gives the opportunity for that care to be integrated with ongoing care by the primary care team of the patients choice. Since the contact details of people who have recently used health services are routinely recorded, the use of the health service utilisation population can potentially enable the health sector to readily identify people who have utilised health services recently but are not yet enrolled in a PHO. Therefore, people who might be missing out on the benefits of PHO enrolment could be better targeted. Since only routine administrative data from the Ministry of Health have been used, the methods can be readily replicated by the Ministry of Health, District Health Boards, and Primary Health Organisations.The estimated resident population used as a denominator in the standard calculation of PHO enrolment is one of two common population outputs from Statistics New Zealand, namely the census usually resident population, and the estimated resident population. These two populations are often misunderstood by the health sector; they should not be used interchangeably. The differences between the two concepts and how they should be used are discussed in the appendix.MethodsIn Aotearoa New Zealand, virtually all healthcare users are assigned a unique alphanumeric code, the National Health Index (NHI), at the time of their first contact with the health care system. The encrypted form of NHI was used in this study to ensure privacy and anonymity of individuals. As all datasets were entirely based on anonymous non-identifiable administrative data, and this work was carried out under the function of DHBs to assess and monitor the needs of their population for services,9 no formal ethical review from the Health and Disability Ethics Committee was required, as per New Zealand ethical guidelines.10The following datasets were sourced from the Ministry of Health. National Minimum Dataset (inpatient hospital events; NMDS, New Zealand coverage) National Non-admitted Patient Collection (outpatients, ED and community visits; NNPAC, New Zealand coverage) Pharmaceutical Collection (PHARMHOUSE, Northern region coverage only) Laboratory Claims Collection (Northern Region coverage only) Primary Health Organisation (PHO) Enrolment Collection, (New Zealand coverage) General Medical Subsidy Data Mart (New Zealand coverage) National Mortality Collection (New Zealand coverage) Master encrypted and secondary encrypted NHI look up list All the unique encrypted NHIs recorded in 2013 from any of the above datasets were merged to form a Health Service Utilisation (HSU) population. The latest domicile code for an individual as recorded in any of the datasets was used to determine the DHB of domicile. The master encrypted and secondary encrypted NHI look-up list was used to ensure any known duplicated encrypted NHIs were not double counted. Effectively, the HSU population includes virtually everyone living in the area covered by the datasets (in this case limited to the Northern region because not all datasets had national coverage) who had a publicly-funded health service contact or was enrolled in PHO in 2013.The HSU population is the inclusion criteria of this study. Ethnicity for the HSU population is derived from the NHI used to link the datasets and in keeping with the New Zealand health sector standard,11 ethnicity was prioritised from multiple ethnic codes in the following order: Maaori, Pacific peoples, Asian, New Zealand European/Other.Aggregated estimated resident population numbers and population projections (MOH version 2013 based on New Zealand Census 2006) were sourced from Statistics New Zealand. This estimated resident population denominator was provided by Statistics New Zealand for the Ministry of Health in November 2013 which was based on projections from the 2006 Census.1. Standard method of calculating the percentage of people enrolled in a Primary Health OrganisationCalculating PHO enrolment rate using the standard method typically involves using the number of people enrolled in an area of interest divided by the corresponding estimated resident population in the same time period of interest. The numerator and denominator are not individually linked.Definitions: Denominator: Estimated resident population from Statistics New Zealand in 2013 by age, gender, ethnicity and DHB. Numerator: The corresponding number of people enrolled by age, gender, ethnicity and DHB as per PHO enrolment 2013 Quarter Three. Quarter Three coincides with the annual June population estimate from Statistics NZ for the relevant year. 2. Alternative indicator: Percentage of people enrolled in a PHO within the CMDHB Health Service Utilisation population in 2013The denominator is the Health Service Utilisation (HSU) population in 2013 derived as described above from record linkage of Ministry of Health datasets via encrypted NHI. The HSU population for this study were defined as below: people who were domiciled in Counties Manukau in 2013, and enrolled in a PHO, or had a publicly-funded health service contact in 2013, namely inpatient and outpatient services, pharmaceutical dispensing, community laboratory test, GMS claims, and were still alive at 31 December 2013. The numerator is the number of people who were enrolled in a PHO (anywhere in New Zealand) at some point during 2013, as determined by record linkage at encrypted NHI level within the HSU population. The HSU population is the inclusion criteria of the study population and the PHO enrolment status is determined for each individual within the HSU population via encrypted NHI linkage between the PHO enrolment data and HSU population. Since the numerator and denominator are individually linked, the ethnicity and demographic variables in the study were identical for an individual, based on the NHI used for linkage, so the numerator-denominator mismatch described in previous reports is eliminated.12 Note that ethnicity in the PHO register may differ from the ethnicity recorded in the NHI, and this study uses the NHI ethnicity for an individual to avoid numerator denominator mismatch.Six quarters of PHO enrolment (2013 Q1\u20134, 2014 Q1\u20132) were used to determine the enrolment status in 2013, based on the starting date of enrolment, because some of the 2013 enrolment statuses were subsequently recorded late, in the 2014 PHO enrolment datasets.3. Subgroup analysis:a. The percentage of people discharged from either of the two key inpatient facilities for CMDHB: Middlemore Hospital (MMH) and Manukau Surgical Centre (MSC) in 2012 and 2013 who were not enrolled within one month of discharge.Definitions: Denominator: Number of people who were discharged from CMDHB hospital facilities in 2012 and 2013 (casemix acute, arranged and elective discharges). People who died within one month of discharge were excluded. Note: One individual may be discharged more than once in a year. Numerator: The number of people discharged from MMH and/or MSC who were not enrolled (anywhere in New Zealand) based on the date of enrolment in 2012 and 2013 as recorded in the PHO enrolment data within a month of hospital discharge. Four quarters of PHO enrolment data in the relevant year and the first two quarters of PHO enrolment data in the subsequent year were examined. The start date of enrolment as recorded in the PHO enrolment record was used. The latest/end date of enrolment determines the latest quarter that an individual is present in the PHO data. The cut off dates for financial claims were used; eg, if an individual is last present in Q1 then it is assumed the person is enrolled on 20 November in the previous year, Q2: 20 February in the year of interest, Q3: 20 May, Q4: 20 August. b. A simplified annual method of estimating the percentage of enrolment can be carried out by determining whether people discharged (excluding deaths) in 2013 were enrolled in the 2014 Q2 PHO enrolment, or not.Definitions: Denominator: Number of people with CMDHB hospital casemix discharges in 2013 excluding death. Numerator: Out of people who were discharged from CMDHB hospital facilities in 2013, the number of people who enrolled in 2014 Q2 nationally (Cut-off date: 20 February). ResultsStandard method of calculating PHO enrolment:Comparing the population estimates released from Statistics New Zealand with the PHO enrolment data at a high level suggests PHO enrolment for the CMDHB population had a coverage of 97% in a snapshot view at Quarter Three that coincides with the annual June population estimate, 2013. The estimated percentage of PHO enrolment is the number of people enrolled, divided by estimated resident population from Statistics New Zealand in CMDHB in the corresponding age group in 2013.Females of child-bearing age appear to have a relatively high level of enrolment (Table 1). Males between the ages of 15 to 29 appear to have a lower level of enrolment. In the older age groups, there are more people enrolled than the Statistics New Zealand population estimates.Table 1: Estimated PHO enrolment rate for the CMDHB population in 2013 by age by the standard method Age (years) Number of people enrolled as per 2013 Q3 PHO enrolment register Estimated Resident Population from Stats NZ in 2013 Estimated PHO enrolment rate (standard method) Females Males Females Males Females Males 0-4 20,183 21,339 20,460 21,440 99% 100% 5-9 20,439 21,727 20,060 21,060 102% 103% 10-14 18,971 19,975 19,460 20,430 97% 98% 15-19 18,918 19,066 19,660 20,270 96% 94% 20-24 19,135 18,048 19,800 20,960 97% 86% 25-29 17,987 15,447 18,230 18,020 99% 86% 30-34 17,538 14,719 17,540 15,510 100% 95% 35-39 17,058 14,533 16,990 14,730 100% 99% 40-44 18,796 16,621 19,220 16,730 98% 99% 45-49 17,830 16,863 18,340 17,090 97% 99% 50-54 16,576 15,618 17,170 16,050 97% 97% 55-59 13,603 13,001 13,940 13,480 98% 96% 60-64 11,571 11,076 11,810 11,180 98% 99% 65-69 9,466 9,061 10,010 9,390 95% 96% 70-74 6,965 6,461 7,190 6,610 97% 98% 75-79 4,826 4,209 4,930 4,170 98% 101% 80-84 3,573 2,673 3,500 2,690 102% 99% 85-89 2,180 1,404 2,030 1,260 107% 111% >90 1,228 492 1,200 500 102% 98% Overall 256,843 242,333 261,540 251,570 98% 96% When enrolment is compared across ethnic groups, Maaori PHO enrolment appears to be much lower that might be expected when compared to estimated resident population from Statistics New Zealand (89% enrolment in Quarter Three 2013) (Table 2). On the other hand, Pacific PHO enrolment is much higher than the number expected based on the corresponding estimated resident population (111% enrolment in CMDHB). This pattern of PHO enrolment for CMDHB is generally consistent with the overall New Zealand pattern for people of these ethnicities (Table 2) and, as discussed subsequently, needs to be considered in the light of likely dataset mismatch in relation to identified ethnicity.Table 2: PHO enrolment rate by District Health Board in New Zealand and ethnicity in Quarter 3 2013, using the standard method DHB Maaori Pacific Asian NZ European & others Overall Auckland 79% 115% 71% 102% 93% Bay of Plenty 93% 93% 93% 99% 97% Canterbury 80% 96% 74% 99% 95% Capital and Coast 86% 99% 79% 96% 93% Counties Manukau 89% 111% 77% 105% 97% Hawkes Bay 92% 96% 90% 99% 97% Hutt 85% 94% 98% 100% 97% Lakes 100% 90% 73% 102% 100% MidCentral 85% 94% 76% 96% 93% Nelson Marlborough 87% 93% 97% 99% 98% Northland 104% 83% 93% 102% 102% South Canterbury 77% 104% 115% 101% 99% Southern 79% 99% 68% 95% 92% Tairawhiti 100% 93% 81% 98% 98% Taranaki 87% 84% 76% 100% 97% Waikato 94% 100% 75% 100% 97% Wairarapa 103% 105% 96% 103% 103% Waitemata 79% 100% 76% 101% 94% West Coast 91% 102% 115% 96% 96% Whanganui 87% 108% 73% 100% 96% Overall New Zealand 89% 106% 76% 100% 96% Alternative indicator: Percentage of people enrolled within the CMDHB Health Service Utilisation population in 2013In CMDHB, out of the people who had contact with publicly-funded health services in 2013, 98% were enrolled at some point in 2013 (Table 3). In other words, only 2% of the Counties Manukau population who had used publicly-funded health services were not enrolled. In contrast to the standard method, the percentage of enrolment was similar across all the selected ethnicities (Table 3). Overall, females had a marginally higher PHO enrolment than males. Pacific people had a marginally lower enrolment rate than Maaori.Table 3: Percentage of PHO enrolment within the CMDHB Health Service Utilisation population in 2013 by ethnicity Ethnicity Enrolled Not enrolled Number of people in the CMDHB health service utilisation population Percentage of enrolment Maaori 85,436 1,457 86,893 98.3% Pacific 130,985 3,150 134,135 97.7% Asian 97,302 2,357 99,659 97.6% NZ European & Others 198,228 3,472 201,700 98.3% Overall 511,951 10,436 522,387 98.0% Using the HSU population as a denominator, children aged 0\u20134 years had one of the lowest rates of PHO enrolment (Table 4).Table 4: Percentage of PHO enrolment within the CMDHB Health Service Utilisation population by summarised age groups and gender Age (years) Females Males Enrolled Not enrolled Number of people in the CM HSU population % of enrolmt Enrolled Not enrolled Number of people in the CM HSU population % of enrolmt 00-04 20,979 719 21,698 96.7% 22,361 802 23,163 96.5% 05-14 40,434 592 41,026 98.6% 42,575 665 43,240 98.5% 15-24 39,170 910 40,080 97.7% 37,887 1,141 39,028 97.1% 25-44 72,848 1,255 74,103 98.3% 62,503 1,921 64,424 97.0% 45-64 61,281 785 62,066 98.7% 57,821 1,025 58,846 98.3% 65 & over 29,027 334 29,361 98.9% 25,065 287 25,352 98.9% Overall 263,739 4,595 268,334 98.3% 248,212 5,841 254,053 97.7% The PHO enrolment rate was similar across the four ethnicities using the HSU population as a denominator (Table 5).Table 5: Percentage of PHO enrolment within the CMDHB Health Service Utilisation population by age and ethnicity Age (Years) Maaori Pacific Asian NZ European and others \

Summary

Abstract

Aim

Estimating Primary Health Organisation (PHO) enrolment rates with a Census-derived estimated resident population denominator may provide misleading results because of numerator and denominator mismatch. This study uses the Health Service Utilisation (HSU) population denominator as an alternative.

Method

A HSU population was generated by record linkage of routinely collected datasets from the Ministry of Health via encrypted National Health Index (NHI). We compare PHO enrolment rates by age and ethnicity in Counties Manukau District Health Board (CMDHB) in 2013.

Results

In CMDHB, 98% of people who had utilised publicly-funded health services in 2013 were enrolled in a PHO in 2013. Using the HSU population as a denominator, PHO enrolment rates for Maaori, Pacific, Asian, New Zealand European/Other population groups were 98.3%, 97.7%, 97.6%, and 98.3% respectively. Just under 4% of people discharged from CMDHB inpatient facilities were not enrolled in a PHO within a month from the day of discharge in 2013.

Conclusion

Using the HSU population as a proxy of health services need, PHO enrolment rates were similar across ethnicities in the CMDHB population. Support to improve PHO enrolment coverage would be more efficient if the HSU population were used to target people who are not yet enrolled in a PHO.

Author Information

Wing Cheuk Chan, Public health Physician, Population Health, Counties Manukau District Health Board, South Auckland; Dean Papaconstantinou, Health Analyst, Population Health, Counties Manukau District Health Board, South Auckland; Doone Winnard, Clinical Director, Population Health, Counties Manukau District Health Board, South Auckland.

Acknowledgements

'- Funding: This study was undertaken as a result of work undertaken in the population health team for Counties Manukau District Health Board (CMDHB). -

Correspondence

Wing Cheuk Chan, Counties Manukau District Health Board

Correspondence Email

wingcheuk.chan@cmdhb.org.nz

Competing Interests

All authors were paid employees of CMDHB.

'- - Ministry of Health. The Primary Health Care Strategy. Wellington: Ministry of Health; 2001. Ministry of Health. Enrolling with a Primary Health Organisation. Wellington: Ministry of Health; 2002. Ministry of Health. 2015/16 Maaori Health Plan Template Guidelines. Wellington: Ministry of Health; 2015. Counties Manukau Health. Counties Manukau District Health Board Maaori Health Plan 2014/15: Manukau 2014. Waitemata District Health Broad. Waitemata DHB annual report for the year ended 30 June 2005. Auckland: Waitemata District Health Broad; 2005. Malcolm L. Towards a reliable and accurate ethnicity database at district and national levels: progress in Canterbury. N Z Med J 2010;123:43-8. Mehta S. Health needs assessment of Asian people living in the Auckland region. Auckland: Northern DHB Support Agency; 2012. Statistics New Zealand. Evaluation of administrative data sources for subnational population estimates. Wellington: Statistics New Zealand; 2013. New Zealand Government. New Zealand Public Health and Disability Act 2000. Wellington: New Zealand Government; 2000. National Ethics Advisory Committee. Ethical Guidelines for Observational Studies: Observational research, audits and related activities: Revised edition. Wellington: Ministry of Health; 2012. Ministry of Health. Ethnicity Data Protocols for the Health and Disability Sector. Wellington: Ministry of Health; 2004. Ajwani S, Blakely T, Robson B, Tobias M, M. B. Decades of Disparity: Ethnic mortality trends in New Zealand 1980-1999. Wellington: Ministry of Health and University of Otago; 2003. Statistics New Zealand. Understanding substitution and imputation in the 2013 Census. Wellington: Statistics New Zealand; 2014. Capitation rates from 1 July 2014. Ministry of Health, 2014. (Accessed 21/11/2014, at http://www.health.govt.nz/our-work/primary-health-care/primary-health-care-subsidies-and-services/capitation-rates.) Statistics New Zealand. Understanding and Working with Ethnicity Data. Wellington: Statistics New Zealand; 2005. Burton J, Nandi A, Platt L. Measuring ethnicity: challenges and opportunities for survey research. Ethnic and Racial Studies 2010;33:1332-49. Statistics New Zealand. Coverage in the 2013 Census based on the New Zealand 2013 Post-enumeration Survey. Wellington: Statistics New Zealand; 2014. 2013 Census information by variable: ethnicity. Statistics New Zealand, 2013. (Accessed 21/11/2014, at http://www.stats.govt.nz/Census/2013-census/info-about-2013-census-data/information-by-variable/ethnicity.aspx.) Chan WC, Jackson G, Wright CS, et al. The future of population registers: linking routine health datasets to assess a populations current glycaemic status for quality improvement. BMJ Open 2014;4:e003975. Minister of Health. Newborn Pre Enrolment Toolkit. Wellington: Ministry of Health; 2012. Statistics New Zealand. Estimated resident population 2013: Data sources and methods. Wellington: Statistics New Zealand; 2014. Statistics New Zealand. A Report on the 2006 Post-enumeration Survey. Wellington: Statistics New Zealand; 2007.- -

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