Exercise testing as a long-term predictor of the development of microalbuminuria in normoalbuminuric IDDM patients.
OBJECTIVE
To determine the association between exercise-induced albuminuria and the development of microalbuminuria over 10 years in subjects with insulin-dependent diabetes mellitus (IDDM) who were initially normoalbuminuric.


METHODS
Thirty-two patients with IDDM and a resting urinary albumin/creatinine ratio (UA/UC) < 2.1 mg/mmol (< 15 micrograms/min) were exercised after water loading on a treadmill for 20 min at double their resting heart rate. UA/UC was determined before and after exercise. The exercise test was considered positive if the UA/UC was > 4.3 mg/mmol (> 30 micrograms/min). Results were compared with resting UA/UC after a 10-year follow-up. Persistent microalbuminuria was defined as a UA/UC > 2.1 mg/mmol (> 15 micrograms/min) in each of two early-morning urine collections.


RESULTS
Five patients developed persistent microalbuminuria after 10 years, and four patients were predicted by a positive exercise test. Two patients with positive exercise tests did not develop persistent microalbuminuria. The sensitivity 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 UA/UC was positively associated with the UA/UC after 10 years (P = 0.005, R2 = 0.31). This association was independent of HbA1, systolic blood pressure, body mass index, and duration of diabetes, but HbA1 remained an independent predictor (P = 0.02) of UA/UC at follow-up.


CONCLUSIONS
Exercise testing may be useful for identifying normoalbuminuric IDDM patients who are susceptible to the later development of microalbuminuria.
O'Brien
S F
SF
University Department of Medicine, University of Western Australia, Perth.
Watts
G F
GF
Powrie
J K
JK
Shaw
K M
KM
D000328:Adult; D000419:Albuminuria; D015415:Biomarkers / Q000097:blood / Q000652:urine; D001794:Blood Pressure; D015992:Body Mass Index; D015331:Cohort Studies; D016001:Confidence Intervals; D003922:Diabetes Mellitus, Type 1 / Q000097:blood / Q000503:physiopathology* / Q000652:urine; D003929:Diabetic Neuropathies / Q000503:physiopathology* / Q000652:urine; D003930:Diabetic Retinopathy / Q000503:physiopathology; D005080:Exercise Test; D005260:Female; D005500:Follow-Up Studies; D006442:Glycated Hemoglobin / Q000032:analysis; D006339:Heart Rate; D006801:Humans; D008297:Male; D011237:Predictive Value of Tests; D012044:Regression Analysis; D012680:Sensitivity and Specificity; D013599:Systole; D013997:Time Factors
D015415:Biomarkers; D006442:Glycated Hemoglobin