Flow cytometric analysis of viable bacteria in urine samples of febrile patients at the emergency department.

BACKGROUND: Fast and reliable diagnostics are important in febrile patients admitted to the emergency department. Current urine diagnostics are fast but moderately reliable or reliable but time consuming. Flow cytometry (FC) is a new promising technique in the diagnostics of complicated urinary tract infections by counting bacteria in urine samples. The aim of this study is to improve the FC method by counting only viable bacteria. METHODS: Urine was obtained from 135 consecutive febrile patients at the emergency department. According to protocol regular diagnostic urine tests were performed. In addition, FC counting of viable and non-viable bacteria was executed after staining with thiazole orange and propidium iodide. All test results were compared to the results of urine culture (≥ 105 colony forming units/mL). RESULTS: At a cut-off value of 2.01 × 105 viable bacteria/mL the sensitivity was 100% and specificity was 78.4% (AUC-value 0.955 on ROC-curve). Spearman correlation test exhibited a higher correlation for flow cytometric counting of only viable bacteria than counting of all bacteria (0.59 vs. 0.37). Using ROC-curves, the AUC-values for FC counting of all bacteria, only viable bacteria and Gram staining were respectively 0.935, 0.955, and 0.968 (P > 0.05). CONCLUSION: FC counting of only viable bacteria can predict quickly and reliably positive and negative urine cultures in febrile patients admitted to the emergency department. It can help to improve the speed and accuracy of the diagnostic procedure at the emergency department. © 2017 Clinical Cytometry Society.

Accurate and fast urinalysis in febrile patients by flow cytometry.

BACKGROUND: The urine culture is worldwide accepted as the gold standard in diagnosing urinary tract infections, but is time consuming and costly, other methods are fast but moderately reliable. We investigated whether counting the number of bacteria by flow cytometry could be a fast and accurate method to analyze urine samples in febrile patients at the emergency department (ED). METHODS: Urine samples were obtained from 140 febrile patients at the ED. Urinalysis was performed according to standard procedures. Flow cytometric analysis for bacteria was performed with the Accuri C6 flow cytometer. Diagnostic values were determined at various cut-off points by using urine culture as the gold standard. RESULTS: The highest diagnostic accuracy of urinalysis of bacteria was obtained with flow cytometric analysis (AUC of 0.96). The best cut-off value for bacteria counted by flow cytometry based on the ROC-curve was 3.72 × 106 bacteria/mL, this resulted in a sensitivity of 94.7% and a specificity of 88.2%. CONCLUSIONS: Counting bacteria by flow cytometry has the highest diagnostic accuracy and is superior to other methods in urinalysis in febrile patients in the ED when using urine culture as the gold standard.