Are Triplicate Urine Samples Necessary to Assess Albuminuria?

BACKGROUND/AIMS: Urinary albumin excretion is subject to intra-individual variability. Thus, for research purposes, it is recommended to test three urine samples collected over a short period of time. The objective of our analysis was to check the usefulness of triplicate samples to determine the albuminuric status of diabetic patients. METHODS: We present the results of the non-planned retrospective analysis of 246 triplicate morning urine samples obtained from 95 type 2 diabetics included in three multinational, randomized, double-blind studies. Albuminuria was determined by immunoturbidimetry on fresh samples in the same central laboratory. Microalbuminuria was defined by a urine albumin to creatinine ratio (UACR) between 2.5 and 25 mg/mmol in males and between 3.5 and 35 mg/mmol in females. Concordance was obtained when the second and/or third sample (UACR2 and UACR3) confirmed the albuminuric status obtained from the first sample (UACR1). RESULTS: Considering the first samples, 9% were within the normal range, 35% showed microalbuminuria and 56% showed macroalbuminuria. The overall concordance rate was 95%. The log of UACR was highly correlated between samples. Bland-Altman plots expressed in percent variations between two samples confirmed that the mean variation was low (around 8%) but revealed the scattering of values, 95% being between -60 and +77% of variation between samples. CONCLUSIONS: There is no benefit in repeating morning UACR determination in diabetic patients to accurately categorize a subject as having normo-, micro- or macroalbuminuria. However, in order to accurately quantify albuminuria, repeated determinations are required.