Clinical significance of urinary N-acetyl-beta-D-glucosaminidase and alanine aminopeptidase

Abstract

The excretion of urinary N-acetyl-beta-D-glucosaminidase (NAG) and Alanine Aminopeptidase (AAP) increases with renal damage. The variation in enzyme activity due to the fluctuation of urine flow rate could almost be eliminated by expressing it as the ratio of enzyme activity to urinary creatinine concentration. The urinary enzyme activities increased not only by tubular damage but also by the reduced creatinine clearance due to glomerular injury. The normal reference values of NAG were 2.84 +/- 2.50U/g creatinine for 24-hour urine and 3.23 +/- 2.76U/g creatinine for random urine. The normal reference values of AAP were 9.71 +/- 6.68U/g creatinine for both 24-hour urine and random urine. Although 128 patients were with abnormal enzymuria, only 39.1%, 52.3%, 83.6%, and 86.7% of the patients were with abnormal serum creatinine, serum urea N, creatinine clearance, and urine protein, respectively. In view of the sensitivity, the determinations of urinary NAG and AAP are suitable for early detection of renal diseases.