Automated Systems Evaluated for Diagnosis of Urinary Infections

Rapid diagnostic of urinary tract infections (UTI) is necessary to provide early information about the presence of bacteria and the indication to administer an antibiotic therapy.

Different rapid automated systems have been evaluated as diagnostic tools for UTIs and compared with a semiquantitative plate culture-reference method in a university hospital with a highly complex patient population.

At the University Hospital of Tübingen (Germany) scientists analyzed 2,230 urine samples using three different rapid automated systems for diagnosis of UTIs. In detail, 950 samples were tested using the UroQuick system, 751 samples were analyzed using the BACSYS-40i system, and 572 samples were tested using the UF-1000i system. The three systems were consecutively tested, each over at least two months. Urine samples were collected from patients attending the University Hospital. The results were compared with a semiquantitative plate culture-reference method incubated overnight at 37 °C.

In comparison to the results obtained by culture techniques, the UroQuick (Alifax; Padova, Italy) showed a sensitivity of 73.0% as compared to positive samples and a specificity of 92.8% as compared to negative samples. Similarly, the BACSYS-40i (Sysmex; Kobe, Japan) revealed a sensitivity of 78.8% and a specificity of 61.8%, and Sysmex's other system, the UF-1000i had a sensitivity of 80.9% and specificity of 78.0%. Contaminated urine samples were excluded from the analysis.

Additionally, sensitivity and specificity for the most common UTI-causing microorganisms were analyzed 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. The hands-on time using the automated systems was significantly reduced to approximately 30 seconds per sample, as compared to that of the culture method. However, the main saving in time is obtained for negative samples. In order to gain information about antibiotic susceptibility, the positive tested samples have to be analyzed by culture techniques.

The authors concluded that the currently available automated systems might possibly be helpful to analyze a typical UTI in an ambulant patient population but not for rapid diagnosis of UTIs in a complex population of hospitalized patients. The study was published on November 11, 2011, in the journal Diagnostic Microbiology and Infectious Disease.

Related Links:
University Hospital of Tübingen
Alifax
Sysmex