[Evaluation of the Sysmex UF-1000i flow cytometer for screening of urinary tract infection]

Abstract

Introduction: The urine culture is a huge workload in the Microbiology Laboratory and remains the gold standard for the diagnosis of urinary tract infections. Considering the high prevalence of negative results, the implementation of a reliable screening method could lead to cost saving in the workload, and speed up reporting of negative results.

Methods: We evaluated the usefulness of the flow cytometer UF-1000i in the screening for negative samples than could be excluded from culture. We divided the samples into two groups, Group 1, males and women of childbearing age who were considered positive with a growth ≥ 104 CFU/ml, and Group 2, considered positive with ≥ 105 CFU/ml growth.

Results: On comparing the culture and screening data in the ROC curve, the best sensitivity and specificity points were 53.1 bact/μl for Group 1, and 128.3 bact/μl for Group 2. In Group 1, the sensitivity was 92.2% and a specificity of 60%, a reduction in urine cultures of 46%, with 2.1% false negative (42 samples). In Group 2, the sensitivity was 86%, with a specificity of 87.7%, a culture reduction of 57.5%, and 5.1% false negatives (74 samples).

Conclusion: The incorporating of the UF-1000i cytometer to the screening of urine samples depends on the characteristics of the patients and the definition of positive urine culture. In our case, with only studying bacteriuria, the data on the reduction of workload and the false negatives seriously question this incorporation.

Keywords: Cribado; Infección del tracto urinario; Screening; UF-1000i; Urinary tract infection.