Rapid bioluminescence method for bacteriuria screening

Abstract

A study was performed to evaluate the UTIscreen (Los Alamos Diagnostics, Los Alamos, N. Mex.), a rapid bioluminescence bacteriuria screen. The UTIscreen was compared with three other rapid bacteriuria screens: the Bac-T-Screen (Vitek Systems, Hazelwood, Mo.), an automated filtration device; the Chemstrip LN (Boehringer Mannheim Diagnostics, BioDynamics, Indianapolis, Ind.), an enzyme dipstick; and the Gram stain. A semiquantitative plate culture was used as the reference method. Of the 1,000 specimens tested, 276 had colony counts of greater than 10(5) CFU/ml by the culture method. Of these, the UTIscreen detected 96% (265 of 276) using greater than or equal to 5% of the integrated light output of the standard reading as a positive interpretive breakpoint, the Bac-T-Screen detected 96% (266 of 276), the Chemstrip LN detected 90% (249 of 276), and the Gram stain detected 96% (264 of 276). Of the 214 probable pathogens isolated at greater than 10(5) CFU/ml, the UTIscreen detected 95% (204 of 214), the Bac-T-Screen detected 98% (210 of 214), the Chemstrip LN detected 92% (198 of 214), and the Gram stain detected 98% (209 of 214). The predictive values of negative test results at greater than 10(5) CFU/ml for the UTIscreen, the Bac-T-Screen, the Chemstrip LN, and the Gram stain were 98, 97, 93, and 98%, respectively. The overall specificities at greater than 10(5) CFU/ml for the UTIscreen, the Bac-T-Screen, the Chemstrip LN, and the Gram stain were 70, 48, 51, and 69%, respectively. There were 532 specimens with colony counts of >10(3) CFU/ml, and of these, the UTIscreen, the Bac-T-Screen, the Chemstrip LN, and the Gram stain detected 72, 81, 76, and 73%, respectively. Of the 249 probable pathogens isolated at >10(3) CFU/ml, the UTIscreen, the Bac-T-Screen, the Chemstrip LN, and the Gram stain detected 91, 95, 89, and 93%, respectively. The overall specificities at > 10(3) CFU/ml for these methods were 79, 55, 57, and 78%, respectively. The cost per test for detection was approximately $0.50 for the Chemstrip LN. Overall, the UTIscreen is rapid and easy to perform; its sensitivity compared favorably with those of the other screening methods; it had higher specificity than the Bac-T-Screen and Chemstrip LN; and it allowed for bathing of specimen.