PEDIATRICS Vol. 101 No. 6 June 1998, p. e1
Received Sep 29, 1997; accepted Feb 17, 1998.

From the * Department of Pediatrics, Children's Hospital of
Philadelphia, Pennsylvania, and
Leonard Davis Institute, University
of Pennsylvania, Philadelphia, Pennsylvania.
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/mm3
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
10 colony-forming units per milliliter of urinary tract
pathogen) for each sample. Cost 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 cost 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.
Key words: urinalysis, Gram stain, dipstick, UTI, rapid screening, febrile infants.