RESUMO
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.
