Urinary n-acetyl-beta-glucosaminidase as a screening technique for vesicoureteral reflux

Abstract 

Objective. To determine if urinary N-acetyl-beta-glucosaminidase (NAG) assays could be applied as a screening test for early detection of vesicoureteral reflux.

Methods. Two hundred eighty-eight urine samples from children undergoing voiding cystourethrography (VCU) for a variety of urologic problems were assayed for N-acetylbeta-glucosaminidase using spectrophotofluorimeter techniques. Sample creatinine levels were also determined using an auto analyzer. The urinary NAG to creatinine ratio for each patient was then compared to their VCU results, which were interpreted independently of the assay values and graded according to the International Reflux Classification system. The NAG to creatinine ratios were then classified according to their grade of reflux, and the mean NAG levels, plus one standard deviation, were calculated for each as well as for the nonrefluxing controls. Statistical analysis was done with P values obtained by Student's t-test.

Results. A total of two hundred thirty-two specimens were evaluable with ninety (38.8%) samples collected from refluxing patients and one hundred forty-tw o (61.2%) samples from nonrefluxers. The NAG levels standardized to urine creatinine revealed a mean value among refluxers of 15.514 μmol/g creatinine. This compared with a mean value of 14.611 μmol/g creatinine in the nonrefluxing group, with the difference being insignificant. When the mean NAG levels were compared for each grade of reflux to the nonrefluxing controls, only grade V had a significant elevation (44.561 μmol/g creatinine) above the nonrefluxers (P = 0.0001).

Conclusions. With the exception of grade V vesicoureteral reflux, urinary NAG levels do not reliably detect the presence of reflux and therefore cannot be accurately applied as a screening test for detection of this common urologic problem.

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