Background: Urine analysis is one of the most common tests for assessing urinary-tract infections, which are the most frequently occurring infectious diseases in community populations. Urine culture is still the ‘gold standard’ for the detection of urinary tract infection, however, it is time- and labor-intensive and and has a high number of unnecessary cultures. The aim of this study was to evaluate the analytical and diagnostic performance of a new urinalysis system LabUMat with UriSed (77 Elektronika, Budapest, Hungary) in comparison to urine culture as the reference method.
Methods: By comparing the test results for 965 urine samples with quantitative urine cultures, we established cut-off criteria for the UriSed. The cut-off values by the receiver operating characteristic (ROC) curve technique, sensitivity, and specificity were calculated for bacteria (BACT) and white blood cells (WBCs).
Results: A bacterial cutoff value of 375/µL provided the best discrimination for community-acquired urinary tract infection, with a sensitivity of 96.5% and a specificity of 82.1% compared with 182 urine culture positive samples (AUC: 0.939). It was possible to forgo 62.6% of cultures with only 8 false-negative results. The best cut-off value for WBCs was 13/µL. When we used an algorithm in which the combination with the positivity for 85 BACT/µL and for 13 WBCs/µL count, the sensitivity and NPV improved to 99.8% and 100%, respectively, but the specificity declined from 78.8% to 52.0%.
Conclusions: When screening with the UriSed for community-acquired urinary tract infection, a cut-off value of 85 bacteria/µL and 13 WBCs/µL should be adopted. Diagnostic performance of UriSed is satisfactory and use of this instrument is a reliable method for screening out a major part of the culture negative samples. It would improve the efficiency of microbiology laboratory, and unnecessary antibiotic prescriptions could be reduced.
DOI: Clin. Lab. 2012;58:107-111