Evaluation of Forward Laser Light Scatter Technology as a Preculture Screen of Unpreserved Urine Specimens

Abstract Introduction Urine cultures are standard of care for the diagnosis of urinary tract infections. Reflexively culturing specimens only after an effective screening test could minimize the number of samples cultured, improving laboratory efficiency. We evaluated a commercial forward laser light scatter system as a screening tool for urine cultures. Methods One hundred ninety (190) consecutive unpreserved urine specimens were screened by the BacterioScan 216Dx system (BacterioScan) prior to urine culture. Performance characteristics were compared against traditional culture methods. Results Urine specimens from 40 men and 150 women were evaluated. In total, 182 specimens were obtained by clean-catch, 7 by catheter, and 1 via nephrostomy; 134 specimens were negative by urine culture (70%). Fifty-six were positive, with the most commonly identified organism being E coli (35 specimens, 62.5%). Compared to urine culture, forward laser light scatter identified 132 positives and 58 negatives (31%) for a sensitivity of 98%, specificity of 42%, positive predictive value of 42%, negative predictive value of 98%, and an overall accuracy of 59%. Average time from collection to result for light scatter analysis was 25 hours and 28 minutes (95% CI, ±74 minutes) versus 52:37 (±280 minutes) for urine culture (P < .01). Time to negative results was 25:51 (±77 minutes) for light scatter versus 53:17 (±320 minutes) for culture (P < .01). Time to positive results was 26:36 (±66 minutes) versus 51:02 (±146 minutes) for culture (P < .01). Conclusions Time to negative result and assay sensitivity showed an improvement over direct urine culture and could reduce number of cultures by ~30%; however, low positive predictive value and accuracy would lead to reflexive culture in the majority of specimens tested, limiting overall utility. Cost analyses may prove the modest efficiency gains do not outweigh the additional expense.