Nitroblue Tetrazolium(NBT) Test as a Screening Test of Urinary Tract Infection in Children

ABSTRACT

PURPOSE: It has been reported that the Nitroblue Tetrazolium(NBT) test is more accurate than the urine pH, leukocyte esterase and nitrite test as a screening test of urinary tract infection (UTI). The purpose of this study is to compare the NBT test with other screening tests and evaluate the clinical usefulness of the NBT test as a screening test. METHODS: We selected 298 results out of the 304 urine cultures which were performed from March, 1999 to July, 1999 and compared them with screening tests such as NBT, urine pH, leukocyte esterase and nitrite tests. We interpreted those results as the urinary tract infection when the screening results were urine NBT(+), pH(>6.5), leukocyte esterase(>or=++) and nitrite(+). RESULTS: Urine NBT, pH and leukocyte esterase tests showed the statistical significance in comparison with the urine culture results(chi-square tests; P<0.001, <0.05, <0.001), while urine nitrite tests did not show statistical significance. As time passing, the sensitivity of 10 min, 30 min, 60 min NBT test was increased to 35%, 72%, 80% respectively but the sensitivity of urine pH and leukocyte esterase was as low as 33%, 16% respectively. But, the specificity of NBT test was reduced from 93% to 53% as the time went by, while the specificity of urine pH and leukocyte esterase tests were as high as each 79%, 96% respectively. Urine NBT tests at 10 min and 30 min showed a higher positive and negative predictive value than those of the other screening tests. CONCLUSION: Urine NBT test as a screening test for UTI was more accurate than the urine pH, nitrite and leukocyte esterase tests. But we think that we should develop a more quick and precise screening test in the future, because of the long time it requires to perform it.