Diagnostic Yield of Timing Blood Culture Collection Relative to Fever

Pediatr Infect Dis J. 2016 Aug;35(8):846-50. doi: 10.1097/INF.0000000000001189.


Background: Conventional practice involves obtaining a blood culture during or immediately after a fever to increase diagnostic yield. There are no data to support this practice in children.

Methods: Retrospective single-center case-control study of children (0-18 years) who had blood cultures performed as part of routine care. Cases had an a priori defined pathogen isolated from blood culture (n = 410) and were age-matched with contemporaneous controls with a sterile blood culture (n = 410). The predictive value of fever (before and after blood culture), C-reactive protein and hematologic indices were analyzed by multivariate regression and area under the receiver operating characteristic curves (AUCs) in neonatal, general pediatric and pediatric oncology patients.

Results: One thousand one hundred seventy-two (6.7%) of 17,607 blood cultures were positive, of which 410 (35%) cultured pathogen(s). Three hundred and twenty four (79%) cases and 275 (67.1%) controls had a fever (≥37.5°C) during the 12 hours pre- or post-collection. Fever 2-6 hours before a blood culture was neither sensitive nor specific for predicting bacteremia in neonatal or pediatric patients and marginally predictive in oncology patients (AUC 0.59-0.63). Cultures obtained 2-6 hours before fever were nonpredictive in neonates (AUC 0.56-0.59), marginally predictive in pediatric patients (AUC 0.64-0.67) and moderately predictive in oncology patients (AUC 0.70). C-reactive protein was marginally predictive in neonates (AUC 0.60). Hematologic indices were nonpredictive in all groups.

Conclusions: Fever before obtaining blood culture was neither sensitive nor specific for culture positivity; timing of pediatric blood cultures relative to fever is unimportant. Bacteremia precedes a fever, but this is of limited clinical applicability.

MeSH terms

  • Adolescent
  • Bacteremia / complications
  • Bacteremia / diagnosis*
  • Bacteremia / epidemiology
  • Blood Culture / methods*
  • Blood Specimen Collection / methods*
  • Case-Control Studies
  • Child
  • Child, Preschool
  • Fever / diagnosis*
  • Fever / etiology
  • Humans
  • Infant
  • Infant, Newborn
  • ROC Curve
  • Retrospective Studies
  • Time Factors