Urine Albumin Should Replace Total Protein for the Assessment of Glomerular Proteinuria

Abstract

Urine total protein has long been used in the assessment of renal disease and many methods are in use for its measurement.P The diversity in methods and standardization is reflected in the poor performance of this assay in external quality assurance schemes.Y At all levels of protein excretion albumin is usually a major protein in urine. Studies, particularly on diabetics,' show that low concentration albumin excretion, microalbuminuria, is a marker for and represents an early stage in the development of overt proteinuria and glomerular nephropathy. At low concentrations of total protein in urine, renal proteins such as Tamm Horsfall protein may be the major contributors. Thus, fluctuations in glomerular permeability, which would be detected by changes in urine albumin concentration, may be masked when assessment is made by measuring urine total protein. We have compared total protein and albumin in a series of urines, collected from patients being investigated for, or monitored with, glomerular disease. It has recently been suggested that both total protein and albumin should be routinely measured to assess glomerular damage.s We examine the question: should assay of urine albumin replace that of total protein?