Performance of the Sysmex UF1000i system in screening for significant bacteriuria before quantitative culture of aerobic/facultative fast-growth bacteria in a reference hospital

Abstract

Objective: To evaluate the performance of the Sysmex UF1000i automatic urine screening system in the quantitative culture of fast-growth aerobic/facultative bacteria.

Methods and results: A standard procedure was used to recover fast-growth aerobic/facultative micro-organisms in 1225 samples, applying (Sysmex(®)) flow cytometry for parallel bacteria and leucocyte counts. According to the area under the receiver operating characteristic curve, the optimal cut-off values to detect bacteriuria >10(5) colony forming units (CFU) ml(-1) were 690/μl for bacteria and 38/μl for leucocytes (sensitivity, 92%; specificity, 65%; positive predictive value [PPV], 39%; and negative predictive value [NPV], 97%). The use of a single cut-off point of 150 bacteria μl(-1) to detect significant bacteriuria of >10(5) CFU ml(-1) or of ≥10(4) CFU ml(-1) plus leucocyturia obtained similar results (sensitivity, 89%; specificity, 54%; PPV, 31%; and NPV, 96%) and allowed 45.7% of the samples to be rapidly excluded.

Conclusions: The Sysmex UF1000i system can be adapted for bacteriuria screening by the use of an appropriate cut-off point.

Significance and impact of the study: This screening system significantly reduces the workload and produces very few false positives and negatives.