Clinical Decisonmaking

Selective rather than routine urine testing finds most urinary tract infections in very young infants with fever

Urinary tract infections (UTIs) are the most common serious bacterial infection seen in young febrile infants, occurring in 3 to 10 percent of infants with fever younger than 3 months. Thus, the current recommendation is that doctors test the urine of all such infants for UTI. Instead, many pediatric practitioners test the urine of young febrile infants according to their clinical judgment rather than routinely. Although this approach differs from the recommendations, a recent study found few late diagnoses of UTIs among more than 800 infants whose urine was not initially tested and who were not initially treated with antibiotics. The study was supported in part by the Agency for Healthcare Research and Quality (HS06485, Robert H. Pantell, M.D., principal investigator).

According to the researchers, doctors tend to order urine tests selectively, focusing on younger and more ill-appearing febrile infants and those who have no apparent fever source (such as an ear infection, conjunctivitis, or respiratory tract symptoms). They studied the urine testing practices of 573 pediatricians from 219 practices who evaluated and treated 3,066 infants 3 months or younger with a temperature of 100.4ºF or higher.

Over half (54 percent) of the infants initially had their urine tested, and 10 percent of those tested had a UTI. Infants with the highest fevers were more likely to be tested and to have a UTI. Younger age, ill appearance, and lack of an apparent fever source were associated with urine testing but not with the presence of a UTI. Among 807 patients not initially tested or treated with antibiotics, only 2 had a subsequent documented UTI, and both did well.

Male infants who were not circumcised had nearly 12 times the likelihood of UTI, females had 5 times the likelihood of UTI, compared with circumcised infants, and infants with a fever lasting 24 or more hours had 80 percent greater odds of developing UTI. However, these factors were not associated with urine testing. The researchers conclude that urine testing should focus particularly on uncircumcised boys, girls, the youngest (bacteremia rates among infants with a UTI in the study ranged from 6 percent in 2- to 3-month-old infants to 17 percent in infants younger than 1 month) and sickest infants, and those with persistent fever.

More details are in "Urine testing and urinary tract infections in febrile infants seen in office settings," by Thomas B. Newman, M.D., M.P.H., Jane A. Bernzweig, Ph.D., John I. Takayama, M.S., M.P.H., and others, in the January 2002 Archives of Pediatric and Adolescent Medicine 156, pp. 44-54.

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