Urinary N-acetyl-beta-D-glucosaminidase as a diagnostic marker of acute pyelonephritis in children

ABSTRACT

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. 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. 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]. 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