Urinary N-Acetyl-Beta-D-Glucosaminidase as a Diagnostic Marker of Acute Pyelonephritis in Children

Abstract

Introduction. Prompt diagnosis and localization of pyelonephritis are of great importance in children. The urinary excretion of enzymes, and in particular N-acetyl-beta-D-glucosaminidase (NAG), is considered a simple noninvasive marker for detection of renal tubular dysfunction due to pyelonephritis. This study was performed to determine the diagnostic value of urinary NAG in acute pyelonephritis.

Materials and Methods. In a quasi-experimental study conducted on 72 children with confirmed pyelonephritis, we measured urinary NAG, creatinine, and NAG-creatinine ratio before and after the treatment. Diagnostic values of these parameters were evaluated by considering the patients before and after the treatment as disease-positive and disease-negative groups, respectively.

Results. The patients were 18 boys (25.0%) and 54 girls (75.0%) with a mean age of 43.0 ± 39.0 months. The mean levels of urinary NAG were 12.20 ± 6.14 U/L and 5.46 ± 7.98 U/L before and after the treatment, respectively (P < .001). The sensitivity and specificity of urinary NAG-creatinine ratio for diagnosis of pyelonephritis were 73.6% and 77.3%, respectively, with a cutoff point of 10.16 U/g (area under the curve = 0.76, 95% confidence interval, 0.67 to 0.76). Significantly higher levels of urinary NAG were found in those who had a negative urine culture at diagnosis (8.8 ± 10.4 U/L) compared to those with a positive urine culture (4.5 ± 8.7 U/L).

Conclusions. We concluded that urinary NAG is elevated in children with pyelonephritis and it can be considered as a further criterion in the diagnosis of upper urinary tract infection.