Urinary tract infection (UTI) is a serious bacterial infection when it occurs in infants three months of age or younger. It may occur in up to 10 percent of this age group. The usual signs and symptoms of UTI that occur in older infants are absent in this age group and, if present, tend to be nonspecific. Because of the inability of physicians to accurately diagnose UTI secondary to these nonspecific signs and symptoms, the current recommendation is to perform urine testing in infants three months of age or younger who present with a fever. Recent information has questioned the need for routine urine testing in infants. Past studies have not supported physicians using their discretion in ordering urine tests. Newman and colleagues determined the predictors and results of urine testing of young febrile infants seen in office settings. In addition, they studied the frequency and impact of late discovery of UTI among patients who did not receive initial urine testing.

The design was a prospective cohort study of infants in 573 practices involved in the Pediatric Research in Office Settings practice-based research network. Infants three months of age and younger with temperatures of 38°C (100.4°F) were evaluated and treated according to the judgment of their physicians. Data collected included demographic information and results of the initial physical examination, which included diagnostic impression and assessment of overall severity of illness before knowing the results of any laboratory tests. Main outcomes measured included urine testing results, early and late diagnosis of UTI, and UTI with bacteremia.

A total of 3,066 infants were enrolled in the study. Of these, 54 percent had urine testing initially, and 10 percent of those were diagnosed with UTI. Infants who were younger, ill-appearing, or had no identified source of fever were more likely to undergo urine testing but were not more likely to have UTIs. Lack of circumcision in males, female gender, and fever of longer duration were associated with UTI. Bacteremia accompanied UTIs in 10 percent of cases and was more likely to occur in the patients younger than one month. A total of 807 infants did not receive urine testing initially, and only two of them developed subsequent UTIs. Both did well with treatment.

The authors conclude that physicians ordered urine testing in infants who were younger, who appeared ill, and who did not have an apparent source of fever. This selective use of urine testing with close follow-up was associated with few late-diagnosed UTIs. The authors also state that urine tests should be performed in uncircumcised boys, girls, the youngest and sickest infants, and infants with persistent fever.