Introduction: Urinary tract infection (UTI) diagnosis by urine culture is time- and labor- consuming. In the Ibn Rochd microbiology laboratory, up to 70% of urine culture samples yield no growth or insignificant growth.
Objective: To evaluate the new generation of Sysmex UF-4000i fluorescence flow cytometry analyzer with a blue semiconducting laser as a method to rule out negative urine samples for UTI, in comparison of urine culture.
Material and methods: Flow cytometry and microbiological analysis were performed on 502 urine samples included in the study. We used ROC analysis to determine cutoff points at which optimal sensitivity and specificity are achieved for clinical use.
Results: Our results showed that bacteria count at a cut-off of 100/μL, and/or the leucocytes count ≥ 45/μL are the optimal indicator for positive culture results. At these cut off, bacteria sensitivity (SE), specificity (SP), Positive predictive value (PPV) and negative predictive value (NPV) were 97,3%, 95%, 87,8% and 98,8% respectively. For leucocytes, SE, SP, PPV and NPV were 99,1%, 95,8%, 88,6% and 99,7% respectively.
Discussion and conclusion: The bacterial and leucocytes counts generated by UF-4000i analysis may be useful in our context as a rapid screening to exclude UTI by reducing about 70% of urines cultures and then workload. Nevertheless, further validation is needed for different patient groups especially with urological disease or immunocompromised patients.
Keywords: ROC analysis; cut-off; flow cytometry; urine culture.