Evaluation of the Sysmex UF-1000i® urine flow cytometer in the diagnostic work-up of suspected urinary tract infection in a Dutch general hospital

Abstract

Background: Automation and standardization of sediment analysis of urine samples by flow cytometry might serve as an alternative to labor-intensive laboratory methods, such as microscopic examination and culture. The Sysmex UF-1000i is a urine flow cytometer that uses two separate channels for counting blood cells and bacteria. Methods: In this study, 358 urine samples were analyzed with the Sysmex UF-1000i in parallel with manual microscopy, Gram stain and bacterial culture, the latter considered the gold standard. Results: Reproducibility for detection of white and red blood cells and bacteria was good, while detection of yeast proved unreliable. Depending on the definition of urinary tract in-fection (UTI) used, the negative predictive value and the per-centage of false-negative results were 100% and 0% [UTI ≥ 105 colony forming units (CFU)/mL] and 99% and 1.3%, (UTI ≥104 CFU/mL), respectively. Pre-screening with the Sysmex UF-1000i would have resulted in a reduction of bacterial culture by 42%. Carry over of bacteria between consecutive samples due to the use of fixed sample needle was observed, but did not result in false-positive interpretation of Sysmex UF-1000i results. Because of the occurrence of carry over, samples that have been analyzed with the Sysmex UF-1000i cannot be used for subsequent urine culture. Conclusions: In conclusion, the Sysmex UF-1000i offers the possibility for screening high numbers of urine samples in a fast and standardized way, resulting in a reduction in workload and speeding the diagnostic process. It is not recommended for use in complicated patient populations, such as neutropenic patients and patients in whom yeast infection is suspected. © 2010 by Walter de Gruyter Berlin New York.