Evaluation of the SediMax automated microscopy sediment analyzer and the Sysmex UF-1000i flow cytometer as screening tools to rule out negative urinary tract infections

Urinary tract infections (UTI) are highly prevalent in nosocomial and community settings, and their diagnosis is costly and time-consuming. Screening methods represent an important advance towards the final UTI diagnosis, diminishing inappropriate treatment or clinical complications. Automated analyzers have been developed and commercialized to screen and rule out negative urine samples. The aim of this study was to evaluate two of these automated analyzers (SediMax, an automatic sediment analyzer and UF-1000i a flow cytometer) to predict negative urine cultures. A total of 1934 urine samples were analyzed. A very strong correlation for white blood cells (WBC) (rs: 0.928) and a strong correlation for bacteria (BAC) (rs: 0.693) were obtained. We also calculated optimal cut-off points for both autoanalyzers: 18 WBC/μL and 97 BAC/μL for SediMax (sensitivity = 96.25%, specificity = 63.04%, negative predictive value = 97.97%), and 40 WBC/μL and 460 BAC/μL for UF-1000i (sensitivity = 98.13%, specificity = 79.16%, negative predictive value = 99.18%). The use of SediMax and UF-1000i resulted in a 46.33% and 57.19% reduction of all samples cultured, respectively. In conclusion, both analyzers are good UTI screening tools in our setting.