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Abstract Aim the aim of this study is to evaluate the accuracy of the HB&L Uroquattro instrument (Alifax, Italy) and the Residual Antimicrobial Activity test (RAA) for rapid and correct diagnosis of Urinary Tract Infections (UTIs) and to compare the results with those obtained with the classical cultural method. Materials and methods A total of 1600 urine samples, collected prospectively from 842 ambulatory patients in Varna city, Bulgaria, were included in the study. All urine samples were tested for bacterial growth and for RAA by HB&L instrument (Alifax, Italy). Simultaneously, each sample was inoculated on Colorex TM Orientation agar and blood, CLED and MacConkey agars. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were determined. Results Among the tested 1600 urine samples, the HB&L instrument detected 343 (21.4%) positive and 1257 (78.6%) negative urine samples. The culture-based method identified 1248 as negative (78%) and 352 urine samples (22%) as positive. The HB&L system correctly identified 343 samples as positive (97.4%) and 1248 samples as negative (100%). The PPV of the rapid automated screening was 100%, and the NPV – 99.3%. The overall accuracy was 99.4%. The positive RAA rate in the whole collection of 1600 urine samples was 5.7% and was detected in 91 patients, all with symptoms of UTIs and recent antimicrobial therapy. In the whole studied group (n = 842), a total of 113 patients reported recent antimicrobial treatment (13.4%). The cultural method demonstrated bacterial growth in 63 patients with positive RAA test, but no pathogens were isolated in 28 patients with RAA detected in their urine samples. Conclusions The screening system demonstrates excellent sensitivity and specificity and, compared to the classical cultural method, has a much faster turnaround time. The RAA test proved a valuable diagnostic tool, particularly in patients with bacteriuria who are under antimicrobial treatment.
Snegarova et al. (Sun,) studied this question.