Urine flow cytometry as a primary screening method to exclude urinary tract infections.
ABSTRACT PURPOSE: To exclude urinary tract infections, culture is the gold standard method, although it is time consuming and costly. Current strategies using dipstick analysis are unsatisfactory as screening methods, because of inadequate sensitivity/specificity. Urine flow cytometry is an attractive alternative. To exclude urinary tract infections, a cutoff value to screen for negative cultures was determined. METHODS: 281 outpatients (51 % male) of a general population visiting the urology department were included. Urine samples were measured by flow cytometry and compared with culture results and dipstick analysis. ROC analysis was performed to evaluate the screening performance of flow cytometry and dipstick analysis compared to culture. RESULTS: 18 % of cultures were positive, defined as >10(4) colony forming units/mL. Bacterial count by flow cytometry alone provides the best sensitivity and specificity to exclude a urinary tract infection. A cutoff value of 60 bacteria/μL urine leads to a sensitivity of 100 % and a specificity of 60 %. Retrospectively, with a cutoff value of 60 bacteria/μL urine, 49 % of the cultures would have been redundant. 20 % of patients receiving antibiotics possibly had received those unnecessarily. The calculated percentage of false negatives was 0 % (95 % confidence interval 0-3.3 %). CONCLUSIONS: Urine flow cytometry is a reliable screening method to exclude urinary tract infections. With a cutoff value of 60 bacteria/μL urine, negative predictive value is 100 % and the calculated percentage of false negatives is 0 % (95 % confidence interval 0-3.3 %). Using flow cytometry as a screening method could lead to a reduction in cultures and antibiotics.
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ABSTRACT: Urinary tract infection (UTI) is one of the most common types of infection. Currently, diagnosis is primarily based on microbiologic culture, which is time- and labor-consuming. The aim of this study was to assess the diagnostic accuracy of urinalysis results from UriSed (77 Electronica, Budapest, Hungary), an automated microscopic image-based sediment analyzer, in predicting positive urine cultures. We examined a total of 384 urine specimens from hospitalized patients and outpatients attending our hospital on the same day for urinalysis, dipstick tests and semi-quantitative urine culture. The urinalysis results were compared with those of conventional semiquantitative urine culture. Of 384 urinary specimens, 68 were positive for bacteriuria by culture, and were thus considered true positives. Comparison of these results with those obtained from the UriSed analyzer indicated that the analyzer had a specificity of 91.1%, a sensitivity of 47.0%, a positive predictive value (PPV) of 53.3% (95% confidence interval (CI) = 40.8-65.3), and a negative predictive value (NPV) of 88.8% (95% CI = 85.0-91.8%). The accuracy was 83.3% when the urine leukocyte parameter was used, 76.8% when bacteriuria analysis of urinary sediment was used, and 85.1% when the bacteriuria and leukocyturia parameters were combined. The presence of nitrite was the best indicator of culture positivity (99.3% specificity) but had a negative likelihood ratio of 0.7, indicating that it was not a reliable clinical test. Although the specificity of the UriSed analyzer was within acceptable limits, the sensitivity value was low. Thus, UriSed urinalysis resuIts do not accurately predict the outcome of culture.Biochemia Medica 01/2013; 23(2):211-7. · 1.87 Impact Factor