title: Value of white cell count in predicting serious bacterial infection in febrile children under 5 years of age.
abstract: OBJECTIVE
  The leukocyte count is frequently used to evaluate suspected bacterial infections but estimates of its test performance vary considerably. We evaluated its accuracy for the detection of serious bacterial infections in febrile children.
  
  
  METHODS
  Prospective cohort study.
  
  
  METHODS
  Paediatric emergency department.
  
  
  METHODS
  Febrile 0-5-year-olds who had a leukocyte count on presentation.
  
  
  METHODS
  Accuracy of total white blood cell and absolute neutrophil counts for the detection of urinary tract infection, bacteraemia, pneumonia and a combined ('any serious bacterial infection') category. Logistic regression models were fitted for each outcome. Reference standards were microbiological/radiological tests and clinical follow-up.
  
  
  RESULTS
  Serious bacterial infections were present in 714 (18.3%) of 3893 illness episodes. The area under the receiver operating characteristic curve for 'any serious bacterial infection' was 0.653 (95% CI 0.630 to 0.676) for the total white blood cell count and 0.638 (95% CI 0.615 to 0.662) for absolute neutrophil count. A white blood cell count threshold >15×10(9)/L had a sensitivity of 47% (95% CI 43% to 50%), specificity 76% (95% CI 74% to 77%), positive likelihood ratio 1.93 (95% CI 1.75 to 2.13) and negative likelihood ratio 0.70 (95% CI 0.65 to 0.75). An absolute neutrophil count threshold >10×10(9)/L had a sensitivity of 41% (95% CI 38% to 45%), specificity 78% (95% CI 76% to 79%), positive likelihood ratio 1.87 (95% CI 1.68 to 2.09) and negative likelihood ratio 0.75 (95% CI 0.71 to 0.80).
  
  
  CONCLUSIONS
  The total white blood cell count and absolute neutrophil count are not sufficiently accurate triage tests for febrile children with suspected serious bacterial infection.
authors.affiliation: Screening and Test Evaluation Program, School of Public Health, The University of Sydney, Sydney, Australia Centre for Kidney Research, The Children's Hospital at Westmead, Sydney, Australia.
authors.forename: Sukanya
authors.initials: S
authors.lastname: De
authors.affiliation: Screening and Test Evaluation Program, School of Public Health, The University of Sydney, Sydney, Australia Centre for Kidney Research, The Children's Hospital at Westmead, Sydney, Australia.
authors.forename: Gabrielle J
authors.initials: GJ
authors.lastname: Williams
authors.affiliation: Screening and Test Evaluation Program, School of Public Health, The University of Sydney, Sydney, Australia School of Public Health and Community Medicine, The University of New South Wales, Sydney, Australia.
authors.forename: Andrew
authors.initials: A
authors.lastname: Hayen
authors.affiliation: Screening and Test Evaluation Program, School of Public Health, The University of Sydney, Sydney, Australia.
authors.forename: Petra
authors.initials: P
authors.lastname: Macaskill
authors.affiliation: Department of Emergency Medicine, The Children's Hospital at Westmead, Sydney, Australia.
authors.forename: Mary
authors.initials: M
authors.lastname: McCaskill
authors.affiliation: Department of Infectious Disease, The Children's Hospital at Westmead, Sydney, Australia.
authors.forename: David
authors.initials: D
authors.lastname: Isaacs
authors.affiliation: Screening and Test Evaluation Program, School of Public Health, The University of Sydney, Sydney, Australia Centre for Kidney Research, The Children's Hospital at Westmead, Sydney, Australia Department of Nephrology, The Children's Hospital at Westmead, Sydney, Australia.
authors.forename: Jonathan C
authors.initials: JC
authors.lastname: Craig
mesh_terms: D001424:Bacterial Infections / Q000097:blood / Q000175:diagnosis*; D002675:Child, Preschool; D015331:Cohort Studies; D004636:Emergency Service, Hospital; D005260:Female; D005334:Fever / Q000382:microbiology*; D005500:Follow-Up Studies; D006801:Humans; D007223:Infant; D007958:Leukocyte Count / Q000379:methods*; D016015:Logistic Models; D008297:Male; D011446:Prospective Studies; D012372:ROC Curve; D012680:Sensitivity and Specificity