Comparison of visual and photometric Bac-T-Screen results

The Bac-T-Screen (Marion Laboratories, Kansas City, MO) was used to screen 826 urine specimens. Of these, 85 either pigmented or clogged the Bac-T-Screen filter and could not be evaluated. Results for the remaining 741 specimens were examined both visually and photometrically by a newly developed photometric card reader. The results were then compared. Screening results for all urines containing greater than or equal to 10(5) pathogens/mL were equivalent for both methods, with sensitivity and predictive negative values of greater than 98% and greater than 99%, respectively. The predictive values of positive tests were also equivalent at 57.5% for visual and 59.6% by photometry. The overall agreement varied with the card reader value used because the photometric card-reader procedure allows the user to select desired sensitivity and specificity levels.