[Can we rely on the results of urine microscopy and culture when tests are performed in general practice?].

INTRODUCTION: Urinary tract infections (UTI) account for 2-5% of consultations in general practice, but only about half the patients with dysuria have significant bacteriuria (> 100,000 bacteria per ml). A microbiological diagnosis can be made by examination of a urine sample, and in Danish family practice the diagnosis of UTI is often reached by a microscopic analysis or a dip-slide culture test. These methods have a high validity when performed in hospital, but we need knowledge about the validity of microbiological urine examinations when performed in general practice. The aim of this study was to validate detection of bacteriuria by urine microscopy and dip-slide culture in general practice.
MATERIAL AND METHODS: Urine specimens artificially produced by adding a known quantity of bacteria (Escherichia coli, Proteus mirabilis, Enterobacter cloacae, Staphylococcus epidermidis and Enterococcus faecalis) to sterile urine were sent to 25 general practices for microscopic examination and dip-slide culture. No prior instruction in testing procedure was given. As the gold standard, the results of a standardised culture method performed by skilled laboratory technicians at the Department of Microbiology, University of Southern Denmark, were used.
RESULTS: Significant bacteriuria was identified by microscopy with a sensitivity of 95% and a specificity of 83%. The corresponding figures for urine culture were 95% and 96%. The morphology of bacteria was interpreted correctly in 80% of microscopic examinations, and 60% of the bacteria strains were classified correctly in terms of their motility. DISCUSSION: The results of urine microscopy and culture performed in general practice are to be relied on.