Process quality of diabetes care under favorable access to healthcare: a 2-year longitudinal study using claims data in Japan

Introductions

Diabetes is one of the most common and costly medical conditions; reducing the disease and its economic burden has become a universal goal in medical care and health policy throughout the world.1 There is evidence that high-quality care and attending physicians regularly reduce the risk of microvascular and macrovascular disease complications and consequently, mortality rates.2–4

The quality of diabetes care can be measured by process measurements including regular glycated hemoglobin (HbA1c) tests, as well as intermediate outcome measures such as achievement of glycemic control.5 Previous studies suggest that patient and healthcare provider factors influence the overall quality of diabetes care.6 Patient factors including access to care influence the quality of diabetes care.7 Some previous studies mention that patient characteristics and comorbid conditions affect the quality of diabetes care,8 ,9 whereas one study shows that women are less likely to be monitored for eye complications.10 In addition, dropout from care (referred to as ‘dropout’ or ‘the dropout patients’ hereafter) is a problematic issue in diabetes care.11 ,12 Dropouts have no access to care, which leads to poor glycemic control through the lack of proper medical care, especially lack of medications.3 Among healthcare provider factors, physicians' beliefs, attitude, and knowledge of diabetes care affect glycemic control and clinical practice directly.13 Clinical guidelines for diabetes from many organizations recommend regular HbA1c tests, retinopathy screening, nephropathy screening, and lipid profile monitoring.14–16 Previous studies of process measurement and adherence to clinical guidelines have been reported in the USA,17 ,18 Canada,19 Europe,20 ,21 and elsewhere.22–24 These studies show that the ‘evidence–practice gap’ among healthcare providers is still a main barrier to the quality of diabetes care, although the gap is gradually decreasing.17 ,21 ,23

In Japan, patients' access to the health service is generally high because of universal health insurance coverage and a generous benefits package including unrestricted access to almost any provider.25 Therefore, it can provide favorable conditions for regular testing of glycemic control as well as screening of complications in chronic diseases such as diabetes. While diabetes is quite prevalent in Japan (7.2 million adults suffer diabetes, ranked 10th in the world),1 improvement of diabetes care has been a growing challenge among Japan's health service sectors.26 Previous studies have been limited to the elderly population27 and physicians' performance in a single hospital in Japan.28 Moreover, these studies failed to include both dropout patients and healthcare provider factors.

Within this context, this study aimed to assess the process quality of diabetes care in terms of persistent follow-up and routine examinations of glycemic control and other complications under favorable access to healthcare conditions using health insurance claims data.

Research design and methods

Identification of patients with type 2 diabetes and dropouts

In Japan's medical claims system diagnoses of ‘diabetes’ must be recorded on the claim forms to allow reimbursements for diagnostic tests and treatment. Hence, diagnosis data from claim forms have high sensitivity. However, some of the diagnoses are recorded only for reimbursing diagnostic tests for diabetes and hence are not necessarily accurate. Thus, in order to increase the specificity of case detection, we additionally classified patients with diabetes into three groups based on prescriptions during the subject-identification year, as follows: insulin injection (at least one prescription of insulin products), oral antihyperglycemic agents (prescribed for 28 days or more), and no diabetes-related prescriptions. Insulin products were included as ‘A10C’ and ‘A10D’ in the Anatomical Therapeutic Chemical (ATC) classification system managed by the WHO.37 Oral antihyperglycemic agents were included as ‘A10H’, ‘A10J’, ‘A10K’, ‘A10L’, ‘A10M’, ‘A10N’, and ‘A10S’ in the ATC classification system. We excluded ‘voglibose, 0.2 mg’ (A10L) prescriptions because these were also under insurance coverage for prevention of type 2 diabetes. We excluded diagnoses of ‘suspected’ diabetes in the claim forms. A flow diagram showing how we identified patients with type 2 diabetes is shown in figure 1.

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Figure 1

Flow diagram to identify patients with type 2 diabetes.

We identified patients with type 2 diabetes who had regularly visited clinics or hospitals at least every 3 months, regardless of whether or not they were hospitalized, in the subject-identification year. This definition of adherence to follow-up visit was recommended as a quality indicator in a previous study.38 We defined non-adherence to follow-up visits (no visits to the clinic or hospital for 3 months or more) in the quality-reporting year as a ‘dropout’. We assessed inpatient as well as outpatient claims records in the quality-reporting year to identify whether patients adhered to follow-up; we also evaluated the number of tests performed during hospitalization.

Results

Dropout patients and quality indicators

We observed that 1409 patients (10.9%) dropped out in total, and among patients taking medication, 474 (6.4%) dropped out in the quality-reporting year. The crude percentage of quality indicators among the 11 500 patients who were adherent to follow-up visits was 84.6% for ≥1 HbA1c tests per year, 49.2% for ≥1 HbA1c tests per 3 months, 32.8% for eye examinations, and 87.3% for serum lipid tests, respectively. Those for urine microalbumin excretion tests and serum creatinine tests were 12.3% and 84.4%, respectively, among the 10 087 patients without known kidney and vesicoureteral disorders or renal failure. In all, 1167 patients (11.6%) had been tested for both urine microalbumin excretion and serum creatinine. The adjusted percentages of quality indicators among the insulin injection and oral antihyperglycemic agent groups were 76.4% and 63.4% for ≥1 HbA1c test per 3 months, 53.5% and 35.6% for eye examinations, and 21.4% and 15.4% for urine microalbumin excretion tests, respectively (figure 2). ORs for each quality indicator are shown in table 2. ORs among younger patients tended to be lower for the HbA1c test (≥1 per year) and eye examination. Annual HbA1c tests were less common in patients aged 40–49 years than in patients aged 60–69 years (OR 0.77; 95% CI 0.66 to 0.91; p=0.002). The eye examinations rate tended to be lower among men than in women (OR 0.59; 95% CI 0.54 to 0.64; p<0.001), among patients aged 40–49 years than in patients aged 60–69 years (OR 0.56; 95% CI 0.50 to 0.63; p<0.001), and among patients who had consulted only one clinic (OR 0.60; 95% CI 0.55 to 0.65; p<0.001). All rates tended to be lower in patients who received no diabetes-related prescriptions than in those who took oral antihyperglycemic agents (as for urine microalbumin excretion test; OR 0.31; 95% CI 0.27 to 0.37; p<0.001).

Table 2

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Adjusted ORs† for process quality indicators by sex, age, prescription, and types of medical consultation facility

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Figure 2

Adjusted annual percentage of quality indicators by prescription. *Excluding patients with kidney and vesicoureteral disorders or renal failure. †Separate multivariate logistic regression models were constructed for each quality indicator. Percentages were calculated from the logistic regression model parameter estimates and are shown here. HbA1c, glycated hemoglobin.

Discussion

The principal finding of this study was that 6.4% of patients with diabetes taking medication dropped out, and that annual test rates were high for the HbA1c, serum creatinine, and serum lipid tests. In contrast, annual eye examination and urine microalbumin excretion test rates were low even among patients with good adherence to follow-up visits despite universal health insurance coverage and generous benefits packages in Japan. A 2-year longitudinal study design that considered dropouts, a large sample of cases, and medication data was the strength of this study compared with previous Japanese studies.27 ,28 In addition, we included patients in their 20s to 40s who were not adequately represented in earlier studies.

Routine HbA1c examination (≥1 per year) was conducted for most patients, especially in the insulin injection and oral antihyperglycemic agent groups. In these patients, regular testing of HbA1c levels may be required for titrating medications at least once every year. The HbA1c level was checked less frequently in the oral antihyperglycemic agent group than in the insulin injection group. The rates of the serum creatinine and lipid tests were also high. It appeared that both tests were conducted simultaneously with the HbA1c test. Although the JDS guidelines do not recommend an optimal frequency for the serum lipid test, the rate of lipid profile monitoring in Japan was high and comparable to that in the US or European countries.17 ,20

Both annual eye examination and urine microalbumin excretion test rates were lower than the rates for other quality indicators, which was similar to an earlier study.27 The eye examination rates in Japan (35.6% among patients taking oral antihyperglycemic agents) were much lower than in the US (73.4%) and European countries (74.8%).17 ,20 As for patient factors, the rates were lower especially among younger patients, which is compatible with a report from the US.39 On the other hand, the rate was lower in men than in women, which contradicts a report from Italy.10 Although our study population had generally favorable access to healthcare, our findings show that retinopathy is more likely to be overlooked in working-age men than women because male full-time workers with diabetes may not find the time to visit an ophthalmologist owing to the long working hours in Japan.40 Rates were also lower among patients who consulted only one clinic in the subject-identification year. In Japan, eye examinations are performed almost exclusively by ophthalmologists; as a result, patients with diabetes usually needed to be referred to another medical facility.26 Our findings suggest that the referral system between the clinics and ophthalmologists may not work effectively in the primary care setting. Interventions to encourage primary care doctors to use ‘the Standard Diabetes Manual’ developed by Japanese clinical researchers improved the performance of nephropathy screening, but did not improve retinopathy screening.41 Thus, interventions that will facilitate the referral system and enhance retinopathy screening and treatment in patients with diabetes such as written communication systems between primary care physicians and ophthalmologists, are needed.42

The annual urine microalbumin excretion test rate in Japan (15.4% among patients taking oral antihyperglycemic agents) was also much lower than in European countries (59.4%).20 Since the serum creatinine screening was optimal, physicians could have been diagnosing nephropathy only from the serum creatinine level, without testing urine microalbumin excretion, which might explain this discrepancy. Early nephropathy may remain undetected owing to such clinical practices. A lack of knowledge among physicians about the efficacy of microalbumin excretion tests or underpayment for these tests may result in this poor performance, despite the JDS guidelines' recommendation of annual urine microalbumin excretion tests. A previous study showed that multifaceted intervention (measuring quality indicators and providing feedback to physicians) was effective for improving the quality of care in primary care settings.38 Development and use of effective multifaceted interventions to improve clinical guideline adherence among physicians is key to preventing nephropathy progression in Japan.

Regarding an international comparison of quality of diabetes care, routine screening of retinopathy and nephropathy in Japan appeared to be poorer than in other developed countries, as discussed above. For instance, our findings suggest that quality indicators for nephropathy screening in Japan were much lower than in the UK; 75.6% of patients with diabetes taking medication were compliant with the UK National Institute for Health and Care Excellence guideline during 2007–2012.43 We suspect that the difference in medical care systems may be one of the reasons for this gap. While patients with diabetes in the UK are taken care of by general practitioners who are financially incentivized to provide a high quality of care (based on the UK's Quality and Outcomes Framework),44 ,45 there are no corresponding systems in Japan; Japanese physicians' pay is not dependent on quality of care provided. In addition, physicians could not afford to spend much time in consultation with outpatients because consultation frequencies are generally high in Japan.25 When we consider together these healthcare provider factors, there may be room to reconsider medical care provision systems for chronic disease care in Japan.

In this study, 6.4% of patients with diabetes taking medication dropped out in the quality-reporting year. As the quality of care and glycemic control would presumably deteriorate in dropouts because of less access to care, encouragement may be required to enhance adherence to follow-ups. The Japan Diabetes Outcome Intervention Trial 2 (J-DOIT2) has been launched to reduce dropout and improve clinical outcomes by providing external support to patients and physicians.26 ,38 In addition, all Health Insurance Societies have been required to make health promotion plans using their beneficiaries' health check-up data and health insurance claims data (referred to as ‘Data Health Plans’) since April 2015 to prevent chronic diseases including diabetic complications and to reduce the economic burden.46 For instance, medical consultation encouragement programs for non-consultation or dropouts are included in the ‘Data Health Plans’. Although consultation encouragement programs tend to be mainly focused on recent health practice, considering our results, adherence to clinical guidelines and referral systems among physicians (healthcare provider factors) would also need to be improved to enhance the overall quality of diabetes care in Japan.

Some limitations of our study should be noted. First, our study population consisted of workers working in large companies and factories, and their dependents. Since this could induce the ‘healthy worker effect’, the prevalence of diabetes in this group may have been lower than in the general population. In addition, gender-based differences in retinopathy screening performance may be inferred from the study population. These may affect the generalizability of this study. Second, although we analyzed patient characteristics using prescription data, blood glycemic levels including HbA1c levels for individual patients were unknown. Thus, some patients may have been inappropriately included as patients with type 2 diabetes in this study. This might have led to the underestimation of quality indicators; however, this only applies to patients not on medication. A cross-sectional study reported that the proportion of patients with diabetes treated with diet therapy (no medications) was 19.9% in 2011; these patients were mainly treated by diabetes specialists in Japan.47 Regarding the patients in this study who were not taking medication (42.2%), quality indicators of these patients may be underestimated due to misclassification; our definition may include patients with a tentative diagnosis of diabetes.48 These data should thus be interpreted with caution. Besides, the urine microalbumin excretion test rate may have been underestimated because patients with overt proteinuria were appropriately tested for urinary protein concentration rather than urine microalbumin concentration. Third, we failed to measure several other process quality indicators recommended by the JDS guidelines, including neuropathy screening, foot care practices, or dental examination because of limited claim data.14 Fourth, our definition of dropout may be too strict and lead to misclassification. A previous study defined dropout as over 12 months' non-attendance at the clinic.11 However, a routine visit to the clinic or hospital at least every 3 months was considered to be a reasonable frequency in the Japanese healthcare setting.38

Conclusions

Despite favorable conditions for access to healthcare in Japan, about 6.4% dropout was observed, and the quality of diabetes care in terms of routine screening of retinopathy and nephropathy appeared to be poorer than in other developed countries, even among patients with good adherence to follow-up visits. The suboptimal quality of care might be attributable to healthcare provider factors that affect retinopathy and nephropathy prevention, as well as patient factors such as low access to retinopathy prevention among working-age men with diabetes. These findings substantially advance previous research in this area as a result of the better study design, large sample size, usage of recorded administrative data, longitudinal analysis with medication data, and availability of international comparisons. Encouraging patient consultations and improvement of physicians' adherence to clinical guidelines and/or referral systems could be key in enhancing the quality of diabetes care.