Rapid diagnosis of uncomplicated urinary tract infection with laser flow cytometry

Abstract

Objective: To evaluate the performance of Sysmex UF1000i (Sysmex, Kobe, Japan) in predicting significant bacteriuria on urine culture from urine specimens of women suspected of uncomplicated urinary tract infection (uUTI). Materials and methods: We retrospectively reviewed urine samples from 1680 adult women with lower urinary tract symptoms suggestive of uUTI from urologic clinics for study. Urine analyses were performed with laser flow cytometry (Sysmex UF1000i). Standard urine cultures were performed. The predictive validity for significant bacteriuria (≥ 105 CFU/mL) was analyzed with logistic regression. Receiver operating characteristic (ROC) curve analysis was used to evaluate the best cut-off point for bacteria count (BACT/μL) to predict significant bacteriuria. Results: A total of 651 specimens met the criteria for analysis. The results indicated that the BACT/μL (AUC = 0.94) generated through Sysmex UF1000i outperformed nitrite (AUC = 0.70), leukocyte esterase (AUC = 0.71), and pyuria (AUC = 0.678) in predicting significant bacteriuria. The optimal cut-off point for bacterial count was set at > 357 BACT/μL with sensitivity of 85.61%, specificity of 88.52%, positive predictive value of 91.8%, and negative predictive value of 78.73%. Excluding those specimens with < 357 BACT/μL, we may decrease negative urine culture rate by 36.9%, and miss 14.0% of positive cultures. Conclusion: Laser flow cytometry (Sysmex UF1000i) can help us rapidly identify patients with significant bateriuria in the preanalytical phase urine culture and thus reduce unnecessary use of antibiotics.

Keywords

• bacteriuria
• diagnosis
• female
• laser flow cytometry
• urinary tract infection