Making a presumptive diagnosis of urinary tract infection by using a urinalysis performed in an on-site laboratory

The purpose of our study was to characterize the utility of certain elements of urinalysis, singly or in combination, in identifying children with urinary tract infections (i.e., positive findings on urine culture). Laboratory results for urine specimens subjected to both urinalysis and culture in an on-site outpatient clinic (office) laboratory during a 36-month period were reviewed. All specimens were collected by one of three methods (the midstream void technique, urethral catheterization, or suprapubic aspiration of urine) from children with symptoms to assist in documenting a possible urinary tract infection. Specimen processing by certified technologists was initiated within 10 minutes of collection. Sensitivity, specificity, and positive and negative predictive values were determined for each test or combination of tests. Of 689 specimens, 102 (14.8%) had positive culture results. The combination of dipstick analysis (leukocyte esterase and nitrite tests) and of microscopic examination for bacteria had a sensitivity of 100% and a negative predictive value of 100%. The nitrite test had a specificity of 100% and a positive predictive value of 100%. We conclude that, when properly collected specimens are evaluated promptly by certified technologists, the rate of accuracy in detecting or ruling out a urinary tract infection (i.e., positive findings on urine culture) with certain elements of the urinalysis is high.