Using the Sysmex UF‐4000 urine flow cytometer for rapid diagnosis of urinary tract infection in the clinical microbiological laboratory

Abstract

AbstractBackgroundUrinary tract infections are responsible for a significant worldwide disease burden. Performing urine culture is time consuming and labor intensive. Urine flow cytometry might provide a quick and reliable method to screen for urinary tract infection.MethodsWe analyzed routinely collected urine samples received between 2020 and 2022 from both inpatients and outpatients. The UF‐4000 urine flow cytometer was implemented with an optimal threshold for positivity of ≥100 bacteria/μL. We thereafter validated the prognostic value to detect the presence of urinary tract infection (UTI) based on bacterial (BACT), leukocyte (WBC), and yeast‐like cell (YLC) counts combined with the bacterial morphology (UF gram‐flag).ResultsIn the first phase, in 2019, the UF‐4000 was implemented using 970 urine samples. In the second phase, between 2020 and 2022, the validation was performed in 42,958 midstream urine samples. The UF‐4000 screen resulted in a 37% (n = 15,895) decrease in performed urine cultures. Uropathogens were identified in 18,673 (69%) positively flagged urine samples. BACT > 10.000/μL combined with a gram‐negative flag had a >90% positive predictive value for the presence of gram‐negative uropathogens. The absence of gram‐positive flag or YLC had high negative predictive values (99% and >99%, respectively) and are, therefore, best used to rule out the presence of gram‐positive bacteria or yeast. WBC counts did not add to the prediction of uropathogens.ConclusionImplementation of the UF‐4000 in routine practice decreased the number of cultured urine samples by 37%. Bacterial cell counts were highly predictive for the presence of UTI, especially when combined with the presence of a gram‐negative flag.