UCSF Studies Infants at Risk for Urinary Tract Infections

January 15, 2002
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In a study of more than 3,000 infants with fevers, UCSF researchers found that there is a higher risk for urinary tract infections in uncircumcised boys compared with girls and circumcised boys. The comparisons were 18 percent for uncircumcised boys, 11 percent for girls and 2 percent for circumcised boys.

There also was a higher risk of urinary tract infections (UTI) with bacteremia (bacteria in the blood, which is much more serious because it can be fatal) for uncircumcised boys (2 percent); compared with 1.4 percent of the girls and 0.3 percent of circumcised boys.

The risk of UTI was also higher in infants whose fevers had lasted more than 24 hours.

The UCSF study looked at predictors and results of urine testing of infants under three months old seen in doctors' offices. The researchers found that although practitioners appropriately used other factors like the height of the fever and age of the baby when deciding which infants to test for UTI, they were not more likely to do urine tests on girls or uncircumcised boys.

The study was published in the Jan. 14 issue of Archives of Pediatrics and Adolescent Medicine. Pediatric practitioners ordered initial urine tests selectively, testing the younger and sicker infants and those with no apparent fever source. "Although the practitioners were not more likely to test uncircumcised boys, girls or those with fever for more than 24 hours, we found that these infants are at a higher risk of UTI," said lead author Dr. Thomas B. Newman, UCSF professor of epidemiology and biostatistics and of pediatrics.

The infants were evaluated by practitioners in the American Academy of Pediatrics (AAP) Pediatric Research in Office Settings (PROS) network.

Newman praised the 573 PROS practitioners from 219 practices for collecting the data for the study. "These busy practitioners in the PROS network donated their time to make this study possible," he said. Not all infants had initial urine tests, but the study found that practitioners followed the infants closely, and there were no negative outcomes from UTI missed at the initial visit.

The researchers recommended practitioners should perform more urine tests on higher risk groups but may not need to do urine testing on all patients. Only two of the 807 infants not initially tested or treated with antibiotics were subsequently diagnosed with UTI and both responded well, according to the study. "This suggests that although not testing all infants with fever differs from the usual recommendation, selective testing appears to be safe in the hands of experienced practitioners who closely follow their patients," Newman said.

In conclusion, the study suggested that when infants under three months old and especially under one month old have a fever more than 38.0 degrees C (100.4 degrees F), primary care clinicians should consider testing for UTI, particularly in girls and uncircumcised boys. In addition, results of this study validated the important contribution that pediatricians in office settings can make to research, Newman said.

The study was supported by a grant from the Agency for Health Care Policy and Research with additional support from the Health and Services Administration Maternal and Child Health Bureau.