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 >105 CFU/ml by the culture method. Of these, the UTIscreen detected 96% (265 of 276) using .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 >105 CFU/mI, 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 >105 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 > 105 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 >103 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 >103 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 >103 CFU/ml for these methods were 79, 55, 57, and 78%, respectively. The cost per test for detection was approximately $1.00 to $1.20 for the UTIscreen, the Bac-T-Screen, and the Gram stain and approximately $0.50 for the Chemstrip LN. Overall, the UTIscreen is rapid and easy to perform; its sensitivity compared favorably with those of other screening methods; it had a higher specificity than the Bac-T-Screen and Chemstrip LN; and it allowed for batching of specimens.

Detection of bacteriuria and pyuria by URISCREEN a rapid enzymatic screening test

“…The two other rapid, nonautomated, simple-to-perform urine screening methods that detect both bacterid and leukocytes are the Gram stain and the Chemstrip LN. Although the Gram stain is one of the most rapid, reliable, and inexpensive methods for estimating bacteria at 105 CFU/ml and .1 leukocyte per oil immersion field, it may be difficult to interpret when low numbers of bacteria are present (6). In addition, the procedure can be tedious and time-consuming for the individual examining the specimen, especially because a majority of urine specimens are negative for 2105 CFU/ml and .1 leukocyte per oil immersion field.…”

ACP Best Practice No 167: The laboratory diagnosis of urinary tract infection

“…False negatives may be seen with candida and enterococcal infection and false positives with gross haematuria. [18][19][20]…”