Analyses of the FlashTrack DNA probe and UTIscreen bioluminescence tests for bacteriuria

Abstract

Five hundred urine specimens were selected at random and screened for bacteriuria by a DNA probe method, FlashTrack (Gen-Probe, San Diego, Calif.), and an automated bioluminescence method, UTIscreen (Los Alamos Diagnostics, Los Alamos, N.M.), and the results were compared with those of the semiquantitative plate culture method. The performance of each test versus culturing was evaluated at colony counts of greater than or equal to 10(4), greater than or equal to 5 x 10(4), and greater than or equal to 10(5) CFU/ml. Since the interpretive breakpoint of each test was user selectable, the results were reported as receiver operator characteristic curves. Optimum interpretive breakpoints were determined for each test at each colony count by calculating a performance index that emphasized sensitivity over specificity in a 70:30 ratio. Although both tests had less-than-optimal sensitivities and specificities, the performance of FlashTrack was significantly better than that of UTIscreen at two of the three colony counts (10(4) and 10(5) CFU/ml); however, FlashTrack costs more and is a labor-intensive procedure. Neither method was evaluated for the detection of colony counts of less than 10(4) CFU/ml.