Ann Lab Med 2019; 39(5): 464-469  https://doi.org/10.3343/alm.2019.39.5.464
Performance of the cobas u 701 Analyzer in Urinary Tract Infection Screening
Victoria Ortiz de la Tabla , Pharm.D.1, Gregoria Gázquez , Pharm. D.1, Ana Infante , Pharm.D.1, Coral Martin , Pharm.D.1, Fernando Buñuel , M.D.1, and Félix Gutiérrez , M.D.2,3
1Microbiology Service, Hospital Universitario de San Juan, Alicante, Spain; 2Infectious Diseases Unit, Hospital General Universitario de Elche, Alicante, Spain; 3Department of Clinical Medicine, University Miguel Hernández, Alicante, Spain
Corresponding author: Victoria Ortiz de la Tabla, Pharm.D.
Microbiology Service, Hospital Universitario de San Juan, Carretera Valencia S/N, San Juan de Alicante 03550, Spain
Tel: +34-965-169-529, Fax: +34-965-919-450, E-mail: ortiz_vic@gva.es
Received: November 30, 2018; Revised: January 31, 2019; Accepted: April 10, 2019; Published online: September 1, 2019.
© Korean Society for Laboratory Medicine. All rights reserved.

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract
Background: Negative urine cultures to rule out urinary tract infections (UTI) generate a considerable laboratory workload; thus, a rapid screening test is desirable. We evaluated the performance of a new automated microscopy analyzer, cobas u 701 (Roche Diagnostics International, Rotkreuz, Switzerland) for the screening of UTI, and developed a rule-out strategy to reduce the number of samples requiring culture. We also assessed squamous epithelial cell (SEC) count as a predictor of culture contamination.
Methods: In total, 1,604 urine samples from outpatients were analyzed with cobas u 701 and culture. Bacterial (BAC) and white blood cell (WBC) counts were used for sample interpretation. To determine a useful cut-off point to predict negative cultures, we selected the highest sensitivity and specificity values obtained from ROC curves. Diagnostic accuracy by age and gender was evaluated.
Results: Urine culture showed growth of ≥104 colony forming units (CFU)/mL in 256 samples (16.0%). The highest sensitivity (91.8%) and specificity (68.4%) were obtained for cut-off points of 119 BAC/μL and 22 WBC/μL. The combination of BAC and WBC improved the performance of the rule-out strategy with a low rate of false-negative results (1.5%) and a high negative predictive value (NPV, 97.3%). Fifty-seven percent of the samples would not have required culture. SEC count was a poor predictor of culture contamination.
Conclusions: cobas u 701 can substantially reduce the number of urine samples requiring culture, with a low false-negative rate and a high NPV.
Keywords: Automated microscopy analyzer, cobas u 701, Screening urine samples, Urinary tract infection, Urine culture



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