Clinicians' interpretations of point of care urine culture versus laboratory culture results: analysis from the four-country POETIC trial of diagnosis of uncomplicated urinary tract infection in primary care.
Hullegie S., Wootton M., Verheij TJ., Thomas-Jones E., Bates J., Hood K., Gal M., Francis NA., Little P., Moore M., Llor C., Pickles T., Gillespie D., Kirby N., Brugman C., Butler CC.
Background.: Urine culture at the point of care minimises delay between obtaining the sample and agar inoculation in a microbiology laboratory, and quantification and sensitivity results can be available more rapidly in primary care. Objective.: To identify the degree to which clinicians' interpretations of a point-of-care-test (POCT) urine culture (Flexicult™ SSI-Urinary Kit) agrees with laboratory culture in women presenting to primary care with symptoms of uncomplicated urinary tract infections (UTI). Methods.: Primary care clinicians used the Flexicult™-POCT, recorded their findings and took a photograph of the result, which was interpreted by microbiology laboratory technicians. Urine samples were additionally processed in routine care laboratories. Cross tabulations were used to identify important differences in organism identification, quantification and antibiotic susceptibility between these three sources of data. The influence of various laboratory definitions for UTI on culture were assessed. Results.: Primary care clinicians identified 202/289 urine samples (69.9%) as positive for UTI using the Flexicult™-POCT, whereas laboratory culture identified 94-190 (32.5-65.7%) as positive, depending on definition thresholds. 82.9% of samples identified positive for E. coli on laboratory culture were also considered positive for E. coli using the Flexicult™ -POCT, and susceptibilities were reasonably concordant. There were major discrepancies between laboratory staff interpretation of Flexicult™ photographs, clinicians' interpretation of the Flexicult™ test, and laboratory culture results. Conclusion.: Flexicult™-POCT overestimated the positivity rate of urine samples for UTI when laboratory culture was used as the reference standard. However, it is unclear whether point-of-care or laboratory based urine culture provides the most valid diagnostic information.