Increased sensitivity in detecting renal impairments by quantitative measurement of marker protein excretion compared to detection of pathological particles in urine sediment analysis

Abstract

Positive test strip results, pathological particles in urine and the presence of proteinuria are common findings in nephropathies. A comparison between these methods and renal biopsies became available with the introduction of quantitative measurement of marker proteins (albumin, transferrin, IgG, alpha(1)-microglobulin, retinol binding protein, alpha(2)-macroglobulin, Bence Jones proteins) and standardised urine sediment analysis by flow cytometry or microscopy. A total of 400 urine samples were examined using marker protein patterns, test strips and quantitative sediment analyses. Results from standardised urine sediment analyses were compared with the excretion of renal marker proteins. Increased erythrocyte and leukocyte counts in urine were observed in only 29% and 39% of the samples for which pathological protein excretion was found. The sensitivity in detecting pathological particles in urine sediment, such as casts and/or dysmorphic erythrocytes, was only 19%. Renal biopsies from 65 patients who were classified as pathological were compared with proteinuria and sediment analyses. Increased excretion of marker proteins was found in all cases, whereas only 41% of the cellular urine sediments showed pathological results. Quantitative measurement of marker proteins from both the glomerular and tubular sides should be used upfront as screening parameters for the early detection of renal disorders.