Are triplicate urine samples necessary to assess albuminuria?

Area of Science:

• Nephrology
• Diabetology
• Clinical Chemistry

Background:

• Urinary albumin excretion exhibits significant intra-individual variability.
• Standard practice recommends triplicate urine samples for research to mitigate variability.
• Accurate assessment of albuminuria is crucial for managing diabetic kidney disease.

Purpose of the Study:

• To evaluate the utility of triplicate urine samples for classifying albuminuric status in diabetic patients.
• To determine if repeated measurements enhance the accuracy of categorizing normo-, micro-, or macroalbuminuria.

Main Methods:

• Retrospective analysis of 246 triplicate morning urine samples from 95 type 2 diabetic patients.
• Albuminuria determined by immunoturbidimetry, with microalbuminuria defined by urine albumin-to-creatinine ratio (UACR) thresholds.
• Concordance assessed by confirmation of albuminuric status across sequential samples.

Main Results:

• First samples revealed 9% normal, 35% microalbuminuria, and 56% macroalbuminuria.
• High overall concordance (95%) was observed between triplicate samples for classification.
• While mean variation was low (~8%), individual sample variations ranged widely (-60% to +77%).

Conclusions:

• Triplicate urine samples offer no advantage for categorizing albuminuric status (normo-, micro-, macroalbuminuria) in diabetics.
• Repeated UACR determinations are essential for precise quantification of albuminuria.
• Single measurements may suffice for classification, but not for accurate quantification.