Screening for microalbuminuria in type 2 diabetes: a reconsideration.

To study the effect of timing of urine collection in determination of microalbuminuria in type 2 diabetic patients, timed urine (night time and daytime) as well as spot urine (first morning and random morning) samples were collected from 44 type 2 diabetic patients, 21 with normoalbuminuria and 23 with microalbuminuria. The methods of spot urine albumin expression for microalbuminuria were also compared between albumin concentration (AC) and albumin to creatinine ratio (ACR). Night time albumin excretion rate (AER) was 16 per cent lower and daytime AER was 13 per cent higher than 24-h AER (p<0.001). Forty-one (93%) of both night time and daytime urine samples had results corresponding with 24-h AER. For the spot urine, expression as AC showed a slightly stronger correlation with 24-h AER than expression as ACR. The levels of albumin in random morning urine samples were 50 and 35 per cent significantly higher than those in first morning urine samples when expressed as AC and ACR, respectively. In conclusion, because of low diurnal variation of AER, either daytime or night time urine could be used for screening of microalbuminuria in type 2 diabetes. Since mean albumin levels obtained from random morning urine were higher than those obtained from first morning urine, the cut-off level should be set higher in random morning urine in order to give comparable sensitivity in predicting microalbuminuria. The spot urine, either first morning or random morning urine, had a good correlation with the 24-h AER whether expressed as AC or ACR. Given the cost of the latter, the authors suggested measuring spot urine AC instead of ACR for screening of microalbuminuria in type 2 diabetes.