Urinary tract infections (UTIs) are among the most common bacterial infections. Rapid and accurate diagnosis is essential for guiding appropriate antimicrobial treatment. The Sysmex UF-5000, an automated urine flow cytometer, provides bacterial counts through flow cytometry. This multicenter study aimed to evaluate the diagnostic performance of UF-5000 in detecting UTIs based on bacterial count, stratified by clinical subtype.

Urine samples were retrospectively collected from three hospitals. All specimens were analyzed with the UF-5000 within 2 hours of collection. UTI diagnosis was based on standard urine culture. Diagnostic performance of the UF-5000 bacterial count was assessed using sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV). Subgroup analysis was conducted for cystitis, uncomplicated acute pyelonephritis (APN), and complicated APN.

Out of 556 cases, 468 (84.2%) were culture-positive. Gram-negative bacteria were predominant (69.7%), with E. coli as the most common pathogen. The UF-5000 bacterial count demonstrated strong diagnostic accuracy for UTI (AUC 0.81, cut-off 463.7). By UTI subtype, the diagnostic performance of bacterial count was as follows: Cystitis (n=223, AUC 0.81, Sensitivity 71.1%, Specificity 80.8%, PPV 96.6%); Uncomplicated APN (n=289, AUC 0.81, Sensitivity 81.0%, Specificity 76.9%, PPV 94.1%); Complicated APN (n=44, AUC 0.85, Sensitivity 75.8%, Specificity 90.9%, PPV 96.2%); Overall: (n=556, Sensitivity 76.2%, Specificity 79.8%, PPV 95.2%, NPV 39.0%). Bacterial count distribution significantly differed among UTI subtypes (p = 0.046 for cystitis, p = 0.024 for complicated APN).

The UF-5000 bacterial count shows high sensitivity and specificity in detecting UTI, with excellent positive predictive values across all clinical subtypes. These findings support the utility of UF-5000 as a rapid and reliable tool for UTI screening in clinical practice.