Positive UA a marker for UTI in infants

August 1, 2015

A new study questions the traditional belief that the sensitivity of the urinalysis (UA) for diagnosing urinary tract infection (UTI) is not optimal in young infants.

A new study questions the belief that the sensitivity of the urinalysis (UA) for diagnosing urinary tract infection (UTI) is not optimal in young infants. To explore UA sensitivity in these children, investigators assembled a database of 245 infants aged younger than 3 months from 20 hospitals who had bacteremic UTI with the same pathogenic organism isolated from blood and urine. They collected data on white blood cells (pyuria), bacteria, nitrites, and leukocyte esterase (LE). They defined a positive UA, using American Academy of Pediatrics criteria, as specified levels of pyuria and/or any bacteriuria on the UA.

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Leukocyte esterase had the highest sensitivity (97.6%) followed by pyuria (96%), whereas nitrites had the highest specificity (100%), which was calculated in a separate sample of 115 infants with negative urine cultures. A negative LE and the absence of pyuria were also quite specific (87.8%) in infants with negative urine cultures (Schroeder AR, et al. Pediatrics. 2015;135[6]:965-971).

Commentary: This was a multicenter study organized through the Pediatric Research in the Inpatient Setting network. The authors made the observation that long-held inaccuracy of the urinalysis in predicting UTI in infants may be attributed to false-positive cultures (either representing contamination or asymptomatic bacteria). They suggest that a child with the same organism in both blood and urine presents a true gold standard against which to measure the accuracy of the UA. In that population, the UA does well. In febrile infants aged younger than 3 months, urine samples with greater than 3 WBCs per high-powered field or with a positive LE predicted a positive urine culture. Absence of nitrites predicted a negative culture in a different group of febrile infants. -Michael G Burke, MD

Ms Freedman is a freelance medical editor and writer in New Jersey. Dr Burke, section editor for Journal Club, is chairman of the Department of Pediatrics at Saint Agnes Hospital, Baltimore, Maryland. The editors have nothing to disclose in regard to affiliations with or financial interests in any organizations that may have an interest in any part of this article.