Comparative leukocyte esterase-nitrite and BAC-T-SCREEN studies using single and multiple urine volumes.

The Chemstrip LN and BAC-T-SCREEN filtration systems were used to evaluate 980 urine specimens rapidly for the presence of microorganisms. Multiple volumes of individual specimens were also tested using the BAC-T-SCREEN to determine whether this procedure enhanced test performance. Ninety-nine specimens (10%) could not be processed because of interfering substances or clogging of the BAC-T-SCREEN. Analysis of the remaining 881 samples showed these test results for the Chemstrip LN system: sensitivity, 48%; specificity, 93%; positive predictive value (PPU), 88%; and negative predictive value (NPV), 71%. The BAC-T-SCREEN results using multiple urine volumes were (for 1 mL) sensitivity, 88%; specificity, 98%; PPV, 97%; NPV, 92%; for 2 mL, sensitivity, 94%; specificity, 96%; PPV, 94%; NPV, 96%; for 3 mL, sensitivity, 98%; specificity, 95%; PPV, 93%; NPV, 98%. Analyzing multiple urine volumes permitted detection of 92% of urine samples with colony-forming units of 10(4) or less. The BAC-T-SCREEN system proved superior to Chemstrip LN for detecting microorganisms in urine specimens, and analyzing multiple urine volumes enhanced test sensitivity.