Objective: To evaluate the accuracy of urine microscopy as a predictor of urinary tract infections (UTIs), taking the urine culture as a criterion standard in a pediatric emergency unit.
Methods: Retrospective study in which all medical charts were analyzed for children younger than 15 years who underwent urine culture and sediment tests. Urine microscopy test was considered positive for leukocyturia when there were more than 10 leukocytes per microliter, and bacteriuria test was considered positive when any presence of bacteria was detected at ×40 magnification. The method of sample taking was also recorded.
Results: Of 18,302 consultations of children younger than 15 years, 1173 (6.4%) needed both a urine culture and a urine microscopy. Urine cultures demonstrated that 20.9% of the samples were consistent with the diagnosis of UTI. Bacteriuria and leukocyturia tests had a sensitivity of 87.4% (95% CI, 82.7%-91.0%), a specificity of 94.8% (95% CI, 93.2%-96.1%), a likelihood ratio for a positive test of 16.7 (95% CI, 16.18-17.61), and a likelihood ratio for a negative test of 0.13 (95% CI, 0.12-0.14). Samples taken by sterile methods (suprapubic aspiration and bladder catheterization) had a better positive predictive value than those taken by nonsterile methods (urine bag and midstream clean-catch) without having an adverse impact on the negative predictive value.
Conclusions: Urine microscopy without Gram stain is a good test for predicting the presence of UTIs in children, which supports the use of this screening method in pediatric emergency units.