Quantitative evaluation of periprosthetic infection by real-time polymerase chain reaction: a comparison with conventional methods

Urinary tract infections (UTI) are one of the most common infections in both hospitalised and ambulant patients. Rapid diagnostic of UTIs is necessary to provide early information about the presence of bacteria and the indication to administer an antibiotic therapy. Here we report on a study comparing 3 different rapid automated systems with the semiquantitative plate culture reference method in a university hospital with a highly complex patient population. In total, 2230 urine samples were consecutively tested using the UroQuick (Alifax), the BACSYS-40i (Sysmex), and the UF-1000i (Sysmex) system. In comparison to the results obtained by culture techniques, the automated systems showed a sensitivity of 73.0-80.9% and a specificity ranging between 61.8% and 92.8%. Additionally, sensitivity and specificity for the most common UTI-causing microorganisms were analysed and showed that sensitivity and specificity correlate with the colony forming units of microorganisms in the urine, with a sensitivity of nearly 90% for Gram-negative rods, typical for community acquired UTIs, but a very low sensitivity for Gram-positive bacteria and yeasts. This led us to the conclusion that the currently available automated systems might be rather helpful to analyse a typical UTI in an ambulant patient population but not for rapid diagnosis of UTIs in a complex population of hospitalized patients.