Diagnosis of Bacteriuria and Leukocyturia by Automated Flow Cytometry Compared with Urine Culture

Abstract

Urinary tract infection (UTI) is a widespread disease, and thus, the most common samples tested in diagnostic microbiology laboratories are urine samples. The "gold standard" for diagnosis is still bacterial culture, but a large proportion of samples are negative. Unnecessary culture can be reduced by an effective screening test. We evaluated the performance of a new urine cytometer, the Sysmex UF-1000i (Dasit), on 703 urine samples submitted to our laboratory for culture. We compared bacteria and leukocyte (WBC) counts performed with the Sysmex UF-1000i to CFU-per-milliliter quantification on CPS agar to assess the best cutoff values. Different cutoff values of bacteria/ml and WBC/ml were compared to give the best discrimination. On the basis of the results obtained in this study, we suggest that when the Sysmex UF-1000i analyzer is used as a screening test for UTI the cutoff values should be 65 bacteria/ml and 100 WBC/ml. Diagnostic performance in terms of sensitivity (98.2%), specificity (62.1%), negative predictive value (98.7%), positive predictive value (53.7%), and diagnostic accuracy (73.3%) were satisfactory. Screening with the Sysmex UF-1000i is acceptable for routine use. In our laboratory, we have reduced the number of bacterial cultures by 43%, speeded up their reporting, and decreased the inappropriate use of antibiotics.The urinary tract is the most common site of infection, and urine culture is the standard diagnostic test for urinary tract infection (UTI). The growing need to enhance the performance of urine culture combined with the need to free up resources by rejecting negative samples quickly and economically has drawn attention to solutions that can be used as screening tests to reduce the number of unnecessary culture tests. In this study, we sought to evaluate and optimize the performance of the Sysmex UF-1000i (Dasit) on 703 urine samples submitted at the same time to bacterial culture analysis. MATERIALS AND METHODSA comparison between the Sysmex UF-1000i urinary cytometer and urine culture was conducted on 703 samples, 128 of which (18.2%) were from hospitalized patients and 575 (81.8%) from outpatients. The urine samples were collected in sterile containers using the technique of midstream capture and were processed within 2 h of collection (5, 10). Each sample was divided into two sterile tubes with a vacuum system (Vacutainer; Becton-Dickinson); one tube was used for urine culture and the other for analysis by the Sysmex UF-1000i.The urine culture was performed by sowing 10 l of the urine sample on chromogenic agar plates (CPS agar; bioMérieux) with calibrated loops. CPS agar is a specific medium for isolation of bacteria in urinary samples. It allows identification of several bacteria-Enterobacteriaceae and Gram-positive bacteriaand it contains specific chromogenic substrates for detecting different enzymatic activities. The resulting colonies are well isolated and easily identifiable by differentiating colors (1). All plates were incubated for 24 h at 37°C, and the results were ex...

Analytical and Clinical Evaluation of Sysmex Uf1000i for Automated Screening of Cerebrospinal Fluids Analitička I Klinička Evaluacija Uređaja Sysmex Uf1000i Za Automatski Skrining Cerebrospinalnih Tečnosti

“…The good performance for bacterial load assessment is another important and innovative finding of this study, wherein the UF-1000i displayed an AUC of 0.99, a sensitivity of 1.00 and a specificity of 0.97 at a threshold of 19 bacteria/mL. It is thus likely that the UF-1000i may be reliably used for the routine screening of bacterial load in CSFs, as already suggested for the screening of urinary tract infections (22,23).…”

Standardization of isothermal microcalorimetry in urinary tract infection detection by using artificial urine

“…However, the majority of urine samples sent to the laboratory are negative. Screening methods (e.g., dip stick testing, automated urine flow cytometry, microscopy) for UTI are limited [15][16][17]. In addition, these tests are not being able to replace urine cultures because they neither identify the causal pathogen nor establish antibiotic susceptibility-guided antibiotic treatment.…”

Flow Cytometry Analysis Using Sysmex UF-1000i Classifies Uropathogens Based on Bacterial, Leukocyte, and Erythrocyte Counts in Urine Specimens among Patients with Urinary Tract Infections

“…The first-generation automated FCA instrument, Sysmex UF50 (Medical Electronics, Kobe, Japan) showed variable results, but the next-generation Sysmex UF-500i and UF-1000i instruments have improved sensitivity and specificity, as well as a separate measurement channel for detecting bacteria (15)(16)(17)(18)(19). In urine specimens, FCA identifies and enumerates bacteria, leukocytes, erythrocytes, and other cells.…”

“…In urine specimens, FCA identifies and enumerates bacteria, leukocytes, erythrocytes, and other cells. Culture-negative specimens are identified and ruled out before culture is performed, which reduces the turnaround time, workload, and cost (15)(16)(17). However, the instrument has not been evaluated for its ability to predict uropathogens prior to urine culture.…”