Quality of diabetes care predicts the development of cardiovascular events: results of the AMD-QUASAR study

Abstract

Objective: The QUASAR (Quality Assessment Score and Cardiovascular Outcomes in Italian Diabetes Patients) study aimed to assess whether a quality-of-care summary score predicted the development of cardiovascular (CV) events in patients with type 2 diabetes.

Research design and methods: In 67 diabetes clinics, data on randomly selected patients were extracted from electronic medical records. The score was calculated using process and outcome indicators based on monitoring, targets, and treatment of A1C, blood pressure, LDL cholesterol, and microalbuminuria. The score ranged from 0 to 40.

Results: Overall, 5,181 patients were analyzed; 477 (9.2%) patients developed a CV event after a median follow-up of 28 months. The incidence rate (per 1,000 person-years) of CV events was 62.4 in patients with a score of <15, 41.0 in those with a score between 20 and 25 and 36.7 in those with a score of >25. Multilevel analysis, adjusted for clustering and case-mix, showed that the risk to develop a new CV event was 84% higher in patients with a score of <15 (incidence rate ratio [IRR] = 1.84; 95% confidence interval [CI] 1.29-2.62) and 17% higher in those with a score between 15 and 25 (IRR = 1.17; 95% CI 0.93-1.49) compared with those with a score of >25. Mean quality score varied across centers from 16.5 ± 7.5 to 29.1 ± 6.3. When the score was tested as the dependent variable, it emerged that 18% of the variance in the score could be attributed to setting characteristics.

Conclusions: Our study documented a close relationship between quality of diabetes care and long-term outcomes. A simple score can be used to monitor quality of care and compare the performance of different centers/physicians.

Figure 1

Event-free survival; all patients by group score.

Figure 2

Risk of developing CV events according to quality of care score classes: results of multilevel analyses. Data are crude incidence rates (IRs) and multilevel IRRs adjusted for age, sex, BMI, duration of diabetes, smoking, and history of previous CV event. Squares denote relative risks, and horizontal lines represent 95% CIs. The position of each square indicates the point estimate of the risk associated with a score of <15 (black squares), between 15 and 25 (gray squares), and >25 (white squares). The latter represents the reference category. ‡Total CV events include angina, MI, stroke, transient ischemic attack, coronary revascularization procedures, lower-limb complications, CV deaths; §major CV events include MI, stroke, and CV deaths; ¶lower-limb complications include claudication, ulcer, gangrene, amputation, and aortic-femoral revascularization procedures.