Increased utilization of primary care 5 years before diagnosis of type 2 diabetes: a matched cohort study.

OBJECTIVE To determine whether case subjects who were later diagnosed with type 2 diabetes utilized primary care differently from control subjects who remained free from diabetes. RESEARCH DESIGN AND METHODS We conducted a matched cohort study using the U.K. General Practice Research Database. Case subjects were aged 30-89 years, diagnosed with diabetes, and later prescribed oral hypoglycemic drugs between 1997 and 2000. Control subjects, who were matched for age, sex, and general practice, were not diagnosed with diabetes and not treated with oral hypoglycemic drugs or insulin. RESULTS Data were analyzed for 5,158 case subjects (2,492 women and 2,666 men) and their matched control subjects with a mean age of 63 years. Five years before the date of diagnosis, case subjects consulted more frequently than control subjects (rate ratio [RR] 1.26 [95% CI 1.20-1.33]) and received more prescription items (1.44 [1.36-1.53]). Consultations were increased for a wide range of conditions. The cumulative 5-year prevalence of diagnoses of hypertension or treatment, hyperlipidemia or treatment, obesity, or coronary heart disease or stroke was 66.1% in case subjects and 45.9% in control subjects (1.44 [1.40-1.49]). A medical diagnosis of hyperglycemia or impaired glucose tolerance was highly (>99%) specific for later diagnosis of diabetes. CONCLUSIONS Primary care consultations and drug utilization are increased from 5 years before diagnosis of diabetes. Diagnoses of hypertension, hyperlipidemia, obesity, or coronary heart disease or stroke have moderate sensitivity for subsequent diabetes but are nonspecific. A diagnosis of hyperglycemia has a high specificity for later detection of diabetes.