Screening Tests for Urinary Tract Infection in Infants
ABSTRACT & COMMENTARY
Source: Shaw KN, et al. Screening for urinary tract infection in infants in the emergency department: Which test is best? Pediatrics 1998;101:e1.
A comparison of screening tests and strategies for detecting urinary tract infection (UTI) in infants was performed on a prospective sample of 3873 infants younger than 2 years old who presented to the ED at Children's Hospital of Philadelphia and had a urine culture obtained by urethral catheterization. In this cross-sectional study, subjects (boys younger than 1 year and girls younger than 2 years) presented with fever without an identifiable source or with UTI symptoms. The screening tests studied were: urine dipstick tests for leukocyte esterase or nitrites, enhanced urinalysis (urine WBC determined by hemocytometer plus Gram stain), Gram stain alone, and dipstick plus microscopic urinalysis. The results of these screening tests were compared with urine culture results (positive urine culture was defined as >= 104 CFU/mL). Cost comparisons of screening strategies were performed.
Of the 3873 cultures obtained, 105 (2.7%) were positive. The enhanced urinalysis was the most sensitive (94%) but the least specific (84%) test. The dipstick alone (³ moderate leukocyte esterase or positive for nitrites) had the highest positive predictive value for detection of UTI (61%). The most cost-effective strategy for detecting UTI using their test performance characteristics in a hypothetical population of 1000 children was: dipstick alone, sending a culture on all patients, and treating presumptively all patients with dipstick of more or equal to moderate leukocyte esterase or nitrite-positive. With this strategy, no UTIs would be missed, less than 2% would be treated unnecessarily, and less than 1% would have a delay in treatment. The cost for this strategy was the lowest at $3.70 per patient. If the enhanced urinalysis alone was used as the screening test (only sending a culture when the enhanced urinalysis is abnormal), its greater sensitivity would eliminate many unnecessary cultures, yet its lower specificity would miss a small percentage of infants with UTI, and the cost of this strategy is almost double that of dipstick and culture for all.
COMMENT BY LEONARD FRIEDLAND, MD
Of the screening tests studied, only the urine dipstick can be performed without CLIA certification, and ED personnel can perform this simple, inexpensive test at the bedside. Dipstick alone is an excellent, low-cost screening test, yet it has poor sensitivity. Therefore, catheterized urine cultures must be sent on all infants. Which strategy is best when screening for UTI in infants? The data from this well-designed study suggest that dipstick plus culture should be performed on all patients. If the dipstick is positive for at least moderate leukocyte esterase or nitrites, then the infant should be presumptively treated with antibiotics until the culture results are known.
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