N-acetyl-beta-D-glucosaminidase and beta 2-microglobulin: Prognostic markers in idiopathic nephrotic syndrome

Increased urinary excretion of N-acetyl-beta-D-glucosaminidase (NAG) and beta 2-microglobulin (beta 2M) is considered a marker of tubulo-interstitial disease. This study assessed urinary excretion of NAG and beta 2M in children with nephrotic syndrome (NS), 14 with cortico-sensitive nephrotic syndrome (CSNS), five with cortico-resistant NS (CRNS) and 30 healthy controls matched for sex and age. At onset urinary excretion of NAG was significantly higher in children with CSNS than controls (p=0.0001) but during remission values were superimposable. Conversely in CRNS at onset urinary excretion of NAG and beta 2M was significantly higher than CSNS and remained unchanged at the end of steroid treatment (p < 0.05 and p < 0.01). Urinary NAG values in CSNS were correlated with proteinuria (r = 0.63), serum total proteins (r = -0.54), serum albumin (r = -0.55) and serum cholesterol (r = 0.67). These data suggest that urinary excretion of NAG and beta 2M may be useful as a marker of tubular dysfunction in nephrotic syndromes which often characterises cortico-resistant patients.