Journal of the New Zealand Medical Association, 13-April-2007, Vol 120 No 1252
Health outcomes for diabetes patients returning for three annual general practice checks
Andrew Tomlin, Susan Dovey, Murray Tilyard
The increasing prevalence of diabetes mellitus worldwide has prompted investigations of primary care initiatives aimed to improve the quality of care provided to patients with diabetes.1–8 These initiatives are often facilitated by diabetes registers and general practice networks monitoring the care provided to diabetes patients.9–15 In conjunction with implementing clinical guidelines for improved diabetes care, they constitute quality improvement mechanisms aimed at minimising adverse health consequences for people with diabetes.
There is less research about changes in the health status of patients monitored as part of these initiatives, and evidence of diabetes outcomes is variable, particularly with regard to glycaemic control,16–18 and the proportion of patients achieving targets set in guidelines. Furthermore, results often focus on patients with Type 2 diabetes, due both to its greater prevalence than Type 1 insulin-dependent diabetes, and because of its preventability. The incidence of Type 1 diabetes is also increasing worldwide, however.19
In New Zealand, the Ministry of Health launched a programme in 2000 to monitor and improve care and outcomes for people with diabetes.20 Under this programme, patients are provided with a free annual consultation for their diabetes and, at each review, a doctor or practice nurse collects demographic and clinical data about the patient and their diabetes.
Although diabetes registers were already established in many New Zealand general practices, primary care organisations supplemented these registers with centralised rolls as a key component of the Ministry programme.
South Link Health, an independent practitioner organisation with 498 South Island general practitioner members, established a diabetes review process for their practices in August 2000. We used data from this diabetes register in the current study.
The effectiveness of interventions to improve chronic disease management may be judged by improvements in patient health over several years. In this research, we examine whether there have been significant changes in the clinical health status of Type 1 and Type 2 diabetes patients enrolled on the South Link Health Diabetes Register across the first 3 years of free diabetes health checks. We also determine the proportion of patients achieving treatment target levels for diabetes care in New Zealand and consider changes in outcomes compared with similar initiatives in other countries.
Study data—Patients listed on practice diabetes registers were invited to attend their practice for an initial diabetes review and to give written consent for their data to be used for research and structured feedback reports to practices. General practitioners were reimbursed for the consultation by the Ministry of Health and South Link Health so that visits were free for patients.
At the first diabetes check, and at each subsequent annual review, data relating to patients and their clinical characteristics were entered onto a standard paper data collection form. Demographic information included date of birth, sex, and ethnic group. Clinical data included type of diabetes, year of diagnosis, weight, height, smoking history, HbA1c level recorded within the last 6 months, blood pressure, albumin/creatinine ratio, fasting total cholesterol, triglycerides and high density lipoprotein (HDL) levels, and diabetic therapy.
Information concerning whether the patient was taking an angiotensin-converting-enzyme inhibitor (ACE inhibitor), an HMG-CoA reductase inhibitor (statin) to control lipids, and whether a foot examination had taken place within the last 12 months was also collected along with details of the most recent retinal screening or ophthalmologist examination.
Study groups—In this study, we focused on changes in the health status of two patient groups: patients with Type 1 and Type 2 diabetes. All patients in both study groups had completed at least three diabetes reviews, and analysis was undertaken on repeated measurements for each patient. Initial reviews took place between September 2000 and December 2003 and patients were included if their third review had been completed by December 2005. By this time, 1634 Type 1 diabetes patients and 16,987 Type 2 diabetes patients had presented for a first diabetes examination. Of these, 6211 patients (33.4%) were not due for their third diabetes review by December 2005, and 1572 (8.4%) were overdue.
The current analysis concentrated on the 840 Type 1 patients (51%) and 9998 Type 2 patients (59%) who had completed three diabetes reviews.
Clinical measures—Diabetic therapy groups were defined as insulin only, insulin and oral hypoglycaemics, oral hypoglycaemics only, and diet only. Smoking status was defined in the register as current smoker (smoking within the last 6 months), past smoker, or never smoked.
In this analysis we calculated the proportion of current smokers. We also determined the percentage of patients receiving an eye examination within the last 2 years and a foot examination within the last 12 months, and the proportion of patients prescribed anti-hypertensive and lipid-lowering medication. Body Mass Index (BMI) was calculated as weight (kg) divided by height (cm) squared.
Outcome measures—For interventions in people with diabetes in New Zealand, we determined the percentage of each study group achieving target levels.21 Optimal target levels for cardiovascular disease are HbA1c <7.0%, blood pressure <130/80 mmHg, total cholesterol <4 mmol/L, HDL cholesterol >1 mmol/L, and triglycerides <1.7 mmol/L.
Female patients with an albumin:creatinine ratio ≥3.5 mg/mmol and male patients ≥2.5 mg/mmol were classified as having microalbuminuria. The European Diabetes Policy Group Guidelines were used to classify patients as being at either “low” or “high” risk for microvascular complications.22 Patients with cholesterol <4.8 mmol/L, triglycerides <1.7 mmol/L, and HbA1c <6.5% were classified as at low risk. Those with cholesterol >6.0 mmol/L, triglycerides >2.2 mmol/L, and HbA1c >7.5% were classified at high risk.
Statistical analysis—Differences in clinical and health status measures at the first and third diabetes reviews were estimated using student’s t-tests for paired samples (continuous data) or the Chi-squared test for differences in proportions. Logistic regression analysis was used to examine the relationship between improved glycaemic control and demographic and diabetes treatment variables for patients with Type 1 and Type 2 diabetes separately. The binomial outcome variable was an absolute decrease in HbA1c level of at least 1% from the first to the third review.
Independent variables in the regression models were age, sex, years since diagnosis of diabetes, current smoking status, decrease in BMI between the first and third reviews, and diabetes therapy. The level of significance for statistical tests was 0.05.
At their first diabetes check, the mean age of patients with Type 1 and Type 2 diabetes was 43.8 years and 65.2 years respectively. Males comprised 55.7% of the Type 1 cohort and 50.3% of the Type 2 cohort.
Mean BMI increased between the first and third diabetes reviews in Type 1 patients of both sexes, and decreased for Type 2 females but not for males. The percentage of Type 2 diabetes patients currently smoking decreased from 11.4% to 10.4%, but there was no significant decrease in smoking among Type 1 diabetics (Table 1).
Diabetes therapy for 419 Type 2 patients (4.2%) was changed from diet or oral-medication-only to insulin-only or insulin-and-oral-hypoglycaemics. Twenty-four patients with Type 1 diabetes (2.8%) changed from insulin-only treatment to insulin plus oral hypoglycaemic medication. There were significant increases in the proportion of patients prescribed ACE inhibitors and statins in both diabetes types.
Changes in glycaemic control—As shown in Table 2, there was a significant increase in mean HbA1c levels in Type 2 diabetes patients (7.2 to 7.3%), but not in Type 1 patients (8.4 to 8.5%).
The proportion of patients achieving the New Zealand guideline treatment level for glycaemic control (HbA1c ≤7%) fell from 17.1% to 12.2% for Type 1 diabetes and from 56.1% to 50.2% for Type 2 diabetes. In the Type 2 cohort, the percentage of patients with poor glycaemic control (HbA1c >9%) also decreased from 10.7% to 9.5% (p<0.01).
Figure 1 indicates that improvements in glycaemic control between the first and third diabetes reviews were mostly achieved by patients with initial HbA1c levels of greater than 8%, and that most of the improvement occurred between the first and second annual checkups.
Seventy-one percent of all diabetes patients with HbA1c >8% at the first review, and 79% with HbA1c >9%, responded to treatment with a lowered reading by the third checkup. The mean reduction in HbA1c was from 9.5 to 8.5% and from 10.5 to 8.9% for these two patient groups.
Figure 1. Changes in glycaemic control for patients at the first review
Changes in blood pressure, albumin/creatinine and blood lipid levels—Mean systolic blood pressure levels decreased in Type 2 diabetes patients (141.1 to 139.4 mmHg) and mean diastolic blood pressure in both Type 1 diabetes patients (74.2 to 73.4 mmHg) and Type 2 diabetes patients (79.1 to 77.3 mmHg). There was a significant increase in the proportion of Type 2 patients achieving the guideline level for blood pressure (130/80 mmHg) from 14.5% to 17.5%, but no significant increase in Type 1 diabetics.
Although albumin:creatinine ratios decreased in both patient groups, there was no significant change in the proportion of males or females with microalbuminuria. Blood lipid levels improved in both diabetes types with mean total cholesterol decreasing from 5.2 to 4.9 mmol/L among Type 1 diabetes patients and from 5.4 to 4.9 mmol/L among Type 2 diabetes patients.
Mean HDL levels increased in both patient groups. The proportion of patients at high risk for microvascular complications decreased from 3.7% to 2.0% of Type 1 diabetes patients and from 4.4% to 2.2% of Type 2 diabetes patients. There was no change in the proportion of patients at low risk in either cohort.
Variables associated with improved glycaemic control—Results from multivariable logistic regression analysis of Type 1 and Type 2 diabetes patients showing the likelihood of an improvement in HbA1c level of at least 1% between the first and third reviews are presented in Table 3. Odds ratios were adjusted for age, sex, duration of diabetes, current smoking status, decreases in BMI between the first and third reviews, and diabetes treatment regimen.
For Type 2 diabetes patients, the odds of improved glycaemic control were at least 23% lower for those over 60 years of age than those under the age of 50 years. The odds for patients with a reduced BMI were 82% higher than for those with no reduction.
Table 3. Logistic regression models for improvement in glycaemic control between 1st and 3rd annual diabetes reviews
†For decrease in HbA1c(%) of ≥1%; ‡Between 1st and 3rd diabetes reviews; *Estimate significant at p<0.05.
Patients on insulin or insulin and oral hypoglycaemics were at least seven times more likely to achieve a clinically significant reduction in HbA1c level than patients controlling their diabetes by diet only. For Type 1 diabetes patients, the odds of improved glycaemic control were over 50% lower for patients between the ages of 40 and 60 years than for patients under 40 years of age.
This study demonstrates that the introduction of a structured and systematic general practice review process aimed at improving diabetes care and patient outcomes is associated with significant improvements in the health status of both Type 1 and Type 2 diabetes patients. Mean blood pressure, cholesterol levels, and albumin:creatinine ratio were reduced in both patient groups while the proportion of patients meeting national guidelines for blood pressure, total cholesterol, and HDL increased.
There were significant increases in the proportion of patients prescribed antihypertensive and lipid-lowering medication. Statin-use more than doubled from the first to the third diabetes review. The Type 2 diabetes group also showed improvements in mean BMI, a reduction in patients currently smoking, and increases in the proportion of patients receiving a foot check in the last 12 months and an eye examination in the last 2 years.
These changes are clinically as well as statistically significant. For example, at the first review, 35.5% of patients with Type 2 diabetes had a 5-year cardiovascular event risk of greater than 20%—but in the third review only 18.3% fell into this same high risk group.
If there are 104,000 New Zealanders with Type 2 diabetes20 this result suggests that after 3 years’ engagement in the program, about 18,000 will have moved from high to lower risk of cardiovascular events. There was, however, no overall improvement in glycaemic control in either patient group.
Comparable data from the Swedish National Diabetes Register showed an improvement in mean HbA1c from 7.8 to 7.2% in patients registered with Type 2 diabetes from 1996 to 2003,16 although this finding did not reflect repeated measurements on all patients.
Results from the NHANES surveys of over 8 million Type 2 diabetes patients in the USA, however, showed a mean HbA1c increase from 7.7 to 7.9% from 1988–1994 to 1999–2000.17 In comparison to the Swedish study in which 35% of Type 2 patients were treated with insulin or insulin and oral hypoglycaemic agents by 2003, only 16% of Type 2 diabetics in the South Link Health programme were treated with insulin at the time of the third diabetes review.
In patients changing therapy from diet or oral medicines only to insulin, mean HbA1c decreased from 8.5% to 8.2% thus indicating that more aggressive treatment may be necessary to improve levels of glycaemic control for some patients. Further evidence for this conclusion was provided by the logistic regression analysis which demonstrated that the odds of an improvement in HbA1c of 1% was 10 times greater for patients on insulin and oral drugs than patients treated by diet alone, and 7 times greater for patients using insulin only. In the Type 2 cohort, the results also indicate that deterioration in glycaemic control may reflect the ageing of patients and the increasing duration of diabetes across the 3 study years.
Improvements in glycaemic control were most notable in patients with high HbA1c levels at the first review. General practitioners may have targeted these patients for special attention but whether this was the case is unknown. Under a new initiative, patients with HbA1c levels greater than 8% at their last two diabetes reviews are now provided with an additional review every 6 months. Closer monitoring of lifestyle factors and glycaemic control in these patients is a priority.
This current analysis has some limitations. There is a small likelihood of error in the assignment of diabetes type either by general practitioners or in data entry on the diabetes register. Six patients recorded as Type 1 on the register were on oral medication or diet only and so were reassigned to the Type 2 group. We estimate the error associated with misassignment as small, and no Type 2 patients on diet or oral medications only should be in the Type 1 group.
This study examines health status measures limited to objective measures only—including other indicators of health such as quality of life and social functioning may have provided a more complete assessment of health. Additionally, we cannot entirely attribute the changes we observed to the diabetes review program, as the influence of generally increased awareness of the need to control blood pressure and cholesterol would also have contributed to the results we report here.
The diabetes patients in this study represent a large cohort by international standards and we have focused on repeated measurements of clinical indicators in a cohort of all diabetes patients registered to more accurately ascertain changes in health status due to the introduction of free annual diabetes examinations.
Data collection was standardised across all participating practices and there were few missing data. At the time data was collated for this study, there were 18,621 patients with Type 1 or Type 2 diabetes who had completed a first diabetes review (a quarter of whom had completed four annual examinations), thus enabling future research to include larger cohorts over a greater time span.
New data now being collected for each patient as part of the programme include known diabetic complications and cardiovascular events; low-density lipoprotein (LDL) levels; and whether metformin, sulphonylurea, or other oral medication was administered.
The diabetes annual general practice checks are different from other population-based programs run in general practice because they are focused on longitudinal management of an already diagnosed chronic disease, whereas other programs (such as cervical screening) seek primarily to diagnose new cases.
Population-based programs are not a core function of general practice where the fundamental focus is on individual patient care.23 Indeed, there may be tensions when individual patients fail to perceive benefits from their engagement in a program targeted to benefitting a population. Ways to resolve these tensions require further research.
The quality of care provided to patients participating in the annual diabetes review programme is improving. The number of patients prescribed medication to control high blood pressure and blood lipid levels increased significantly by the third review as did the proportion of patients receiving retinal examinations and foot checks. In addition, there was a decrease in the number of Type 2 diabetes patients currently smoking.
There were significant improvements in some outcome measures including blood pressure, cholesterol, and albumin:creatinine ratio but no evidence of improved glycaemic control in either Type 1 or Type 2 diabetes patients.
Competing interests: None.
Author information: Andrew Tomlin, Research Fellow, Royal New Zealand College of General Practitioners (RNZCGP) Dunedin Research Unit, Dunedin; Susan Dovey, Associate Professor, Department of General Practice, Dunedin School of Medicine, University of Otago, Dunedin; Murray Tilyard, Elaine Gurr Professor of General Practice, Department of General Practice, Dunedin School of Medicine, University of Otago, Dunedin
Acknowledgements: The free diabetes examinations for patients with diabetes were funded by the Ministry of Health and South Link Health. We also thank the patients and doctors who contributed data for this study as well as Theresa McClenaghan (South Link Health) for resolving various data issues.
Correspondence: Andrew Tomlin, RNZCGP Dunedin Research Unit, Department of General Practice, Dunedin School of Medicine, University of Otago, PO Box 913, Dunedin. Fax: (03) 479 7431; email: email@example.com
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