EXERCISE TESTING AS A LONG-TERM PREDICTOR OF THE DEVELOPMENT OF MICROALBUMINURIA IN NORMOALBUMINURIC IDDM PATIENTS

OBJECTIVE - To determine the association between exercise-induced albu minuria and the development of microalbuminuria over 10 years in subje cts with insulin-dependent diabetes mellitus (IDDM) who were initially normoalbuminuric. RESEARCH DESIGN AND METHODS - Thirty-two patients w ith IDDM and a resting urinary albumin/creatinine ratio (U-A/U-C) <2.1 mg/mmol (<15 mu g/min) were exercised after water loading on a treadm ill for 20 min at double their resting heart rate. U-A/U-C was determi ned before and after exercise. The exercise test was considered positi ve if the U-A/U-C was >4.3 mg/mmol (>30 mu g/min). Results were compar ed with resting U-A/U-C after a 10-year follow-up. Persistent microalb uminuria was defined as a U-A/U-C >2.1 mg/mmol (>15 mu g/min) in each of two early-morning urine collections. RESULTS - Five patients develo ped persistent microalbuminuria after 10 years, and four patients were predicted by a positive exercise test. Two patients with positive exe rcise tests did not develop persistent microalbuminuria. The sensitivi ty of the exercise test for the development of microalbuminuria was 80 % (95% confidence interval [CI] 65.8-94.2%) and the specificity was 92 .9% (95% CI 83.9-100%). The postexercise U-A/U-C was positively associ ated with the U-A/U-C after 10 years (P = 0.005, R(2) = 0.31). This as sociation was independent of HbA(1), systolic blood pressure, body mas s index, and duration of diabetes, but HbA(1) remained an independent predictor (P = 0.02) of U-A/U-C at follow-up. CONCLUSIONS - Exercise t esting may be useful for identifying normoalbuminuric IDDM patients wh o are susceptible to the later development of microalbuminuria.