Urinary protein electrophoresis, which analysis to select? A simplified interpretation

Permanent proteinuria is an early marker of the kidney dysfunction. Tracking by urinary strip, imposes a precise quantification by the laboratory. In front of the difficulties of urine collection during 24 hours, protein determination can be carried out on the urine of a miction and can be expressed as g per g of creatinine (uPCR). We analysed the impact of the expression of the proteinuria in g/L (uP) as compared to uPCR on the urinary electrophoretic profiles. A revision and a simplification of this in practice clinical interpretation is proposed. The proteinuria of 696 in-patients was quantified on an Olympus AU2700. The urinary electophoretic profiles (SDS-AGE) were interpreted by two biologists. uP and uPCR are well correlated (r=0.847, p< 0.0001). Data agreed for proteinuria > 1 g/L but concordance was obtained only in 74% of the subjects and 55% of the pathological patients. A repetition of the analyses is suggested. The interpretative diagram suggested with simplified comments improved interpretation. We advise an interpretation by two biologists. In conclusion, interpretation of the urinary electrophoretic profile rests on the rate of total proteinuria. Expression of the proteinuria as gig of creatinine must be associated with the expression in g/L because of the analytical conditions. The SDS-AGE Technique does not allow the identification of the monoclonal compound but allows a quantitative follow-up under treatment and especially an early tracking of the type of renal dysfunction.