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| Journal of the New Zealand Medical Association,
04-August-2006, Vol 119 No 1239
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Investigating the accuracy of ethnicity data in New Zealand
hospital records: still room for improvement
Judith Swan, Steven Lillis, David Simmons
The accuracy of ethnicity information in New Zealand
hospital records has been investigated several times1–3 over the last 24
years. Each of these investigations has demonstrated inadequacies in the
accuracy of ethnicity information contained in
hospital records,
particularly in relation to Māori. Such miscoding can lead to under- or
over-estimates of differences in health outcomes or health resource utilisation
in differing ethnic groups in New Zealand. The accuracy of hospital records is
particularly important, as data from the hospital records constitute one
of the few data sets available to describe morbidity in the New Zealand
context.4
The Barriers to Diabetes Care in the Waikato Study
(Barriers) commenced in 2003. This study was established to identify perceived
obstacles to the provision and receipt of quality diabetes care in the Waikato
region. This study is unique in New Zealand diabetes research in asking the same
questions of both providers and consumers of diabetes care. The structure of the
Barriers Study enables the comparison of perceived obstacles, and possible
solutions, between providers and consumers, between primary and secondary
providers, and between differing geographic and demographic groups.
Once obstacles to care have been identified, strategies can
be planned to improve the delivery of diabetes care in an environment
characterised by rapidly escalating disease burden. This paper reports on one
demographic variable—ethnicity, and extends the knowledge of the accuracy
or otherwise of this information in the hospital records.
MethodsThe Waikato District Health Board (WDHB) catchment area
comprises approximately 8.3% of New Zealand’s land area in the central
North Island. The population count of the WDHB in the 2001 census was 317,751
people, 8.5% of the national population. Two urban areas: Hamilton, a main urban
area, and Tokoroa, a secondary urban area; accommodate 56.8% of the
district’s population.5
Ethnically,
the WDHB population has more people who identify as Māori than the national
population (20.2% and 14.1% respectively), fewer self-identified Pacific people
(2.1%, 5.4%), fewer self-identified Asian people (3.3%, 6.1%), and the same
European / 'Other' people (74.4%).5 This source combines European and
'Other' ethnic groups together, while this paper reports on these groups
separately.
The exact numbers of people with diabetes in the WDHB
region are unknown. The WDHB estimated in 2003 that there were 12,487 people who
live with diabetes in the region. Of these, 5734 (45.9) were
Māori, 6253
(50.1%) were European, and 500 (4.0%) were Pacific people.5 Other similar
estimates have been published.6,7
A validated four-item open questionnaire8 was posted to
people who have diabetes; all general practitioners and practice nurses; all
diabetes staff; and all relevant hospital-based medical, senior nursing, and
allied health staff. The questionnaire asked the participant to identify what
prevents diabetes care, how to improve diabetes care, what worries them about
diabetes care, and to make any other comments. Additional closed questions
elicited demographic and health history information.
Planned follow-up of non-participants was based on
methods described by Dillman.9 The follow-up consisted of posting a second
questionnaire, ‘in person’ follow-up to selected groups, and phone
follow-up for all others. Consent was requested to access hospital records.
As part of the structured questionnaire, a single
question asked “Which ethnic group(s) are you?” Participants could
select, from six
options (European,
Māori, Pacific Island, South Asian, Asian and ‘Other’), and
could list up to three ethnic groups. The order of ethnicities indicated was not
analysed separately.
The hospital record data was drawn from the Regional
Diabetes Database, a standalone National Health Index-based database developed
and managed by the Regional Diabetes Service. This database permits recording of
a single, patient-selected ethnicity.
Ethnicity data from completed questionnaires was
compared with ethnicity information in the hospital-based medical record, for
those who had consented. The self-identified ethnicity, from the Barriers Study,
was taken as the standard, against which the hospital record was compared.
This
paper reports on Māori–non-Māori differences as well as
disaggregating the non-Māori group. In the Māori–non-Māori
comparisons, if Māori was one of the reported ethnic identities, for those
who reported multiple ethnicities, these participants were
counted as
Māori. All the other ethnic identities were grouped together and counted as
non-Māori. In the analysis across all ethnic groups no prioritisation was
applied.
Using percentage and 95% confidence intervals,10 the
results were analysed using self-identified ethnicity and hospital record
ethnicity as the denominator. The accuracy of the hospital record was assessed
using the first analysis, while the latter provides a prediction of an
individual’s ethnicity based on the hospital record material. The study
was approved by the Waikato Ethics Committee.
ResultsThe Barriers questionnaire was sent to 6881 people who live
with diabetes. Of these, 4499 (65.4%) have been received back and 3500 provided
consent to accessing of their hospital record. Ethnicity data from both the
hospital record and the Barriers Study were available for all of these 3500
individual records. Data from these two sources are shown in Table 1.
Table 1. Variation in ethnic identity between
self-identification (Barriers) and hospital
records; Māori
and non-Māori (n=3500)
These
data show that 71.2 (95% CI: 67.2–75.0)% of persons who self-identify as
Māori were correctly recorded as such in their hospital record. For those
who self-identify in a non-Māori ethnic group, 99.3 (98.8–99.7)% were
correctly recorded in their hospital record.
Considering the predictive value of a hospital record of
ethnicity, the
Barriers data showed
that 94.9 (92.2–96.7)% of persons described in their hospital record as
Māori identified themselves as Māori. Similarly, 95.2
(94.4–95.9)% of those described in their hospital records as
non-Māori identified themselves as belonging to a
non-Māori
ethnic group.
Nearly
one in three participants who self-identified as Māori were recorded as
non-Māori in their hospital record. However, examining these 149
participants in more detail reveals a situation that is more complex than just
incorrectly recorded ethnicity. Table 2 describes the diversity of these
participants.
Table
2. Detail of those who self-identify as Māori and whose hospital record
shows non-Māori (n=149)
These data show that two-thirds of this group self-identify
with multiple ethnic groups (11 participants identified with three ethnic
groups). Of those who identified with multiple ethnic groups the majority (88%)
were correctly recorded in the hospital record for one of their ethnic
identities.
When combined with the data from Table 1, this shows that
88.2 (85.2–90.8)% of participants who
self-identify
Māori as one of their ethnic groups had their ethnicity correctly recorded
for one of their ethnic identities. However, this leaves 11.8 (9.3–14.9)%
of participants who self-identify as Māori with their ethnicity incorrectly
recorded in their hospital
record. Most of
these are participants who self-identified solely as Māori.
Closer
examination of the much smaller group of participants who self-identify in a
non-Māori ethnic group but are recorded as Māori in their hospital
record shows 17 of the 20 self-identify as solely European. Two
participants self-identified as solely Pacific Islander. The one remaining
participant identified in two ethnic groups, these being European and Pacific
Islander.
Combining the data from Tables 1 and 2 allows consideration
of ethnic identity across all participants and all of their (sometimes multiple)
ethnic identities. At this level, the data show 97.7 (96.8–98.3)% of
participants had an identical ethnic group recorded for one of the ethnic
identities.
Table 3 shows the data across all the ethnic groups in the
Barriers dataset. While in all groups (except the ‘Other’ group) the
majority of respondents (64.1–89.1%) had the same ethnicity data
self-identified and recorded in the hospital notes, several variations
emerged.
The self-identified ethnic group was correctly recorded in
the hospital record for 89.1 (87.3–90.6)% of Europeans; 67.2
(54.7–77.8)% of Pacific Island ethnic groups; 70.2 (57.3–80.6)% of
South Asian ethnic groups; and 64.1 (48.4–77.4)% of Asian ethnic
groups—but only 41.0 (27.1–56.7)% of ‘Other’ ethnic
groups. Most participants who had their ethnicity recorded differently to their
self-identified status in the 'Other' group had European as their ethnic group
in the hospital record.
Table 3. Variation in ethnic identity between
self-identification (Barriers) and hospital records; all ethnic groups
(n=3500)
The
hospital record predicted the self-identified ethnic group for 94.5
(93.1–95.6)% of Europeans; 94.6 of Māori; and 93.2 (81.2–98.4)%
of Pacific Island ethnic groups. However, for Asian ethnic group participants,
the predictive value of the hospital record fell to 86.2
(68.9–95.2); and to 74.1 (61.0–84.1)% for South Asian ethnic group
participants. The hospital record predicted only 4.5 (2.7–7.2)% of those
who identified in the ‘Other’ ethnic group. Most [78.8
(74.2–82.7)%] respondents recorded in the ‘Other’ ethnic group
self-identified as European.
DiscussionThese findings have significant policy implications. With
such major discrepancies in ethnicity reporting among non-European groups in the
major national outcome dataset (besides death certificates), it is difficult for
the impact of policies focussing on inter-ethnic health disparities to be
interpreted.
The accuracy of self-identified ethnic group hospital
records has been reported on several times by different
researchers.1–3
Table 4 shows how self-identity has compared with hospital records for
Māori and non-Māori over the last 24 years. Our data are consistent
with the two earlier studies, but not Priest and Jackson.
Indeed, one of the earlier reports was from the Waikato.2
Whether our results reflect national coding validity is unknown, but the Waikato
itself is a significant proportion of the national population.
Table 4. Self-identity and correctly recorded ethnic
group in hospital data 1980–2004 in New Zealand; various researchers
Limited information appears to have been published
specifically addressing the accuracy of hospital data for ethnicity variables
elsewhere. Boehmer et al11 reported on a review of a US dental
department’s outpatient clinic files compared with self-reported
race/ethnicity. These authors show that 77.1% of clinic files were correct for
those who self-reported as white. The accuracy fell to 4.6% for those who
identified as American Indian— with accuracy at 68.9% for Black or African
American; 61.0% for Spanish, Hispanic, or Latino; and 54.0% for Asian people.
The accuracy of the clinic records was lower in all ethnic groups when
respondents identified with multiple ethnicities.
Western Australian data from an interview study12 showed
85.8% of indigenous people were correctly recorded in hospital records.
Non-indigenous people had the correct ethnicity recorded in 99.5% of hospital
records.
When comparing these studies it must be noted that each used
a slightly different method for data collection, which may explain some of the
variation in the results shown in Table 4. It is known that ethnic responses may
alter depending on a range of factors, including broad social structures,
perceived fiscal or political benefit, psychological, and familial.13 Technical
issues such as question design, collection methods, timing and coding can also
have an impact.13,14
Notwithstanding these methodological differences, it appears
that ethnic identity has been recorded in
hospital records less
accurately for those who self-identify as Māori than for those
self-identify in a non-Māori ethnic group. Moreover, this situation seems
to be a long-standing tradition which does not seem ready to change. While the
high and rising
levels of
accuracy in the non-Māori ethnic group appears reassuring, this may be
misleading. The Barriers Study data (Table 3) clearly shows that when the
non-Māori ethnic group is disaggregated into its component parts, all
ethnic groups experience mis-recording in their hospital records.
The mis-recording of ethnic identity is particularly
problematic in the ‘Other’ ethnic group, where the predictive value
of the hospital record is also highly suspect. The ‘Other’ group may
require specific attention from data entry personnel to increase the accuracy of
ethnic self identity when people present for hospitalisation.
At more defined levels of ethnic identity there may be
further concerns, not able to be reported on with the Barriers Study data. This
study requested participant information at aggregated levels, thus the study
cannot report on the accuracy of hospital records, for those who identify, for
example, as Tongan or Sri Lankan.
More positively, it is important to note that nearly 98% of
all participants had an ethnic group correctly recorded in the hospital record
for one of their ethnic groups. While multiple ethnic identities do increase the
complexity of demographic analysis, in any field, it is important that effort is
expended to reflect the everyday realities of participants.
Lastly
the predictive value of ethnicity information in hospital records show high
levels of accuracy for Māori, Non-Māori, and Pacific Island ethnic
groups (the latter two at aggregated levels). However there is room for
improvement in the Asian and South Asian ethnic groups. The accuracy of
the hospital record must be questioned when it states an individual belong to
the ‘Other’ ethnic group.
As has been shown by past researchers, hospital records
continue to mis-record ethnicity when compared to self-identified ethnic group.
This occurs for all ethnic groups. The hospital record can predict ethnicity
accurately but only at higher levels of aggregation: more detailed levels of
ethnic group extracted from the hospital record must be treated with caution.
The discrepancies between the self-identified ethnicity and
the ethnic group recorded in hospital record demonstrate several concerns which
researchers, clinicians, and policy makers must be cognisant of. This continuing
limitation of data in the contemporary New Zealand health environment must act
as an impetus to improve the collection and accuracy of all datasets, but
especially hospital records. Hospital data comparing ethnic groups needs to be
viewed cautiously and the implications of misclassification should be reported
quantitatively.
Author information:
Judith Swan, Diabetes Research Fellow; Steven Lillis, Senior Lecturer in General
Practice; David Simmons, Professor of Medicine; Waikato Clinical School,
University of Auckland, Hamilton
Acknowledgements:
The Barriers to Diabetes Care in the Waikato Study was supported with funding
from the Waikato Medical Research Foundation and the Waikato Local Diabetes
Team. The authors also acknowledge the assistance of Dr Jarrod Harr in the
coding process.
Correspondence:
Judith Swan, c/- Barriers to Diabetes Care in the Waikato, First Floor, Hockin
Building, Waikato Hospital, PO Box 934, Hamilton. Fax: (07) 834 3615;
email: judithswan@actrix.co.nz
References:
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