Screening for urinary tract infection in infants in the emergency department: Which test is best?

Objective. Comparison of rapid tests and screening strategies for detecting urinary tract infection (UTI) in infants. Methods. Cross-sectional study conducted in an urban tertiary care children's hospital emergency department and clinical laboratories of 3873 infants<2 years of age who had a urine culture obtained in the emergency department by urethral catheterization; results of urine dipstick tests for leukocyte esterase or nitrites, enhanced urinalysis (UA) (urine white blood cell count/mm plus Gram stain) Gram stain alone, and dipstick plus microscopic UA (white blood cells and bacteria per high-powered field) compared with urine culture results (positive urine results defined as greater than or equal to 10(4) colony-forming units per milliliter of urinary tract pathogen) for each sample. Cast comparison of 1) dipstick plus culture of all urine specimens versus 2) cell count +/- Gram stain of urine, culture only those with positive results. Results. The enhanced UA was most sensitive at detecting UTI (94%; 95% confidence interval: 83,99), but had more false-positive results (16%) than the urine dipstick or Gram stain (3%). The most cost-effective strategy was to perform cultures on all infants and begin presumptive treatment on those whose dipstick had at least moderate (+2) leukocyte esterase or positive nitrite at a cost of $3.70 per child. With this strategy, all infants with UTI were detected. If the enhanced UA was used to screen for when to send the urine for culture, 82% of cultures would be eliminated, but 4% to 6% of infants with UTI would be missed and the cast would be higher ($6.66 per child). Conclusion. No rapid test can detect all infants with UTI. Physicians should send urine for culture from all infants and begin presumptive treatment only on those with a significantly positive dipstick result. The enhanced UA is most sensitive for detecting UTI, but is less specific and more costly, and should be reserved for the neonate for whom a UTI should not be missed at first visit.