AN EXAMINATION OF THE COVARIABILITY OF SUBCLINICAL ALBUMINURIA IN INSULIN-DEPENDENT DIABETES-MELLITUS - IMPLICATIONS FOR MONITORING MICROALBUMINURIA

We examined the covariability of subclinical albuminuria in a cohort o f 160 insulin-dependent diabetics who underwent simultaneous measureme nts of overnight urinary albumin excretion rate (UAV) and several clin ical variables on 7 occasions over a period of 18 months. After allowi ng for within-patient correlation between visits, significant within-p atient associations were found between UAV and variations in tobacco c onsumption (regression coefficient=0.006, S.E.=0.002, P=0.02), insulin dose (regression coefficient=0.003, S.E.=0.001, P=0.01) and creatinin e clearance (regression coefficient=0.776, S.E.=0.047, P < 0.0001); th e association between UAV and creatinine clearance was not influenced by adjusting for urine flow rate. No significant associations were fou nd between UAV and changes in blood pressure, glycaemic control or oth er variables. We then focused on 33 patients with intermittent microal buminuria, defined as a UAV > 30 mu g/min on at least one occasion, bu t not exceeding 3 consecutive occasions. These patients had a total of 52 episodes of microalbuminuria which were significantly associated a t the 5% level with increases in creatinine clearance (P=0.02), but no t with changes in other variables. Our findings did not differ in pati ents with intermittent microalbuminuria defined with reference to a cu t-off UAV of 20 mu g/min. We conclude that changes in glomerular filtr ation rate (as reflected by creatinine clearance) may partly account f or the within-patient variability in subclinical albuminuria in insuli n-dependent diabetics, and that variables routinely measured in the cl inic are not useful for deciding when to monitor patients for microalb uminuria.