Normal and abnormal daily urinary albumin excretion.

Urinary albumin excretion (UAE) is very variable from day to day. We analyz ed day-to-day UAE in 207 elderly (60-75 years) inpatients (134 with and 73 without diabetes mellitus) attending the department of internal medicine of the Angers University hospital. Twenty-four-hour urine was collected 3 times during a 5-10 day hospitalizat ion period. One-hundred-fifty-one patients (73%) displayed normoalbuminuria (UAE <30 mg/24h in 2 or 3 measures) while 56 patients (27%) had microalbum inuria (UAE within 30-300 mg/24h in 2 or 3 measures). As the raw data of UA E was not normally distributed, we transformed UAE into the variable z=log( log(k+UAE)) where k is an integer. We found that z has a gaussian distribut ion for k=2. Mean value and coefficient of variation of z in the 3 measurem ents were used to define the level and the temporal intra-individual variab ility of UAE. Expressed in term of z, the day-to-day intra-individual variability of UAE showed a potent change (from large variability to small variability) at the particular level z=1.25, corresponding to UAE=30.8 mg/24h, which is precis ely the level currently used to define microalbuminuria in diabetic subject s.