Evaluation of the modified Bac-T-Screen and FiltraCheck-UTI urine screening systems for detection of clinically significant bacteriuria.

Previous evaluations of the Bac-T-Screen system (Vitek Systems, Inc., Hazelwood, Mo.) demonstrated excellent sensitivity with specimens from patients with clinically significant bacteriuria (including infections with small numbers of uropathogens) but poor specificity with specimens from noninfected patients. In the study reported here, the sensitivity and specificity of the Bac-T-Screen system with a modified decolorizing reagent were evaluated. A manual filtration system, FiltraCheck-UTI (Vitek Systems), for screening urine specimens, Gram stains of mixed urine specimens, and quantitative cultures were also evaluated. The test sensitivity for clinically significant bacteriuria was greater than 96% with the original Bac-T-Screen system as well as the modified system and the manual system. In comparison, the sensitivities of the Gram stains and quantitative cultures (greater than or equal to 10(5) CFU/ml) were 82 and 77%, respectively. Of the 375 patients classified as noninfected by clinical parameters, 34% had positive screening tests with the original Bac-T-Screen system, as compared with 13 and 11% with the modified Bac-T-Screen and FiltraCheck-UTI systems, respectively. Thus, the modified Bac-T-Screen system and the manual FiltraCheck-UTI system have sensitives comparable to that of the original Bac-T-Screen system and markedly improved test specificities.