Rapid urinalysis assays for the diagnosis of urinary tract infection.

Urinary tract infection (UTI) in premenopausal women is a frequent complaint in general practice. UTI is usually diagnosed on the basis of clinical symptoms and the use of one or more laboratory tests, the most common being rapid urinalysis reagent assays (urine dip) or midstream urine culture. In order to correlate the leucocyte esterase results of a rapid urinalysis assay with direct urine microscopy for pyuria, undiluted non-centrifuged urine samples from 206 volunteer female healthcare professionals were subjected to analysis using direct urine microscopy using a counting chamber and a rapid urinalysis assay. Of the 206 specimens, 74 were positive for leucocyte esterase using the rapid urinalysis assay, and 39 specimens demonstrated significant pyuria (greater than or equal to 10 leucocytes/microl) on direct microscopy. When the leucocyte esterase results were correlated with the direct urine microscopy results, an assay reading of 15 leucocytes/microl ('trace' on the visual scale) had a sensitivity of 91%, specificity of 79%, positive predictive value of 53% and a negative predictive value of 97%. An assay reading of 25 leucocytes/microl ('+' on the visual scale) or greater had a sensitivity of 63%, specificity of 95%, positive predictive value of 75% and a negative predictive value of 91%. In premenopausal, non-pregnant females, a rapid urinalysis assay result of 25 leucocytes/microl or greater will predict significant pyuria on urine microscopy with reasonable confidence, thereby reducing the need for more costly urine cultures.