Diagnostic testing for serious bacterial infections in infants aged 90 days or younger with bronchiolitis.

OBJECTIVES: To describe the different laboratory tests that are performed on young infants aged 90 days or younger with bronchiolitis and to identify historical and clinical predictors of infants on whom laboratory tests are performed.

DESIGN: Cross-sectional study whereby information was obtained by retrospective review of medical records from November through March 1992 to 1995 of all infants with a clinical diagnosis of bronchiolitis.

SETTING: Urban pediatric emergency department.

PATIENTS: Two hundred eleven consecutive infants aged 90 days or younger (median age, 54 days) with 216 episodes of bronchiolitis.

MAIN OUTCOME MEASURES: Historical and clinical data on each infant in addition to laboratory data that included a white blood cell count, urinalysis, and blood, urine, and cerebrospinal fluid cultures.

RESULTS: Two or more laboratory tests (not including chest radiographs) were obtained in 48% of all infants and 78% of febrile infants. Of the 91 infants with a history of a temperature of 38.0 degrees C or more or temperature on presentation of 38.0 degrees C or more, white blood cell counts were obtained in 77%, blood cultures in 75%, urinalyses in 53%, urine cultures in 60%, and analyses-cultures of cerebrospinal fluid in 47%. Febrile infants were 10 times more likely to get at least 2 laboratory tests than afebrile infants (P<.01). All 6 studies were done in 42 (58%) of 72 febrile infants compared with 7 (16%) of 43 afebrile infants (P<.001). Multiple logistic regression analysis identified a history of a temperature of 38.0 degrees C or more or temperature on presentation of 38.0 degrees C or more (odds ratio [OR] 10.0; 95% confidence interval [CI], 4.8%-21.0%; P<.001), oxygen saturation less than 92% on presentation (OR, 4.7; 95% CI, 1.9%-12.1%; P<.01), and history of apnea (OR, 0.1; 95% CI, 0.02-0.35; P<.001) as significant clinical predictors of whether laboratory studies were obtained. History of preterm gestation, aged younger than 28 days, previous antibiotic use, and presence of otitis media were not associated with obtainment of laboratory studies. No cases of bacteremia, urinary tract infection, or meningitis were found among all infants with bronchiolitis who had blood, urine, and/or cerebrospinal fluid cultures.

CONCLUSION: There is wide variability in the diagnostic testing of infants aged 90 days or younger with bronchiolitis. The risks of bacteremia, urinary tract infection, and meningitis in infants with bronchiolitis seems to be low. History or a documented temperature of 38.0 degrees C or more; oxygen saturation of less than 92%, and history of apnea were associated with laboratory testing for bacterial infections.