title: Lack of Accuracy of Biomarkers and Physical Examination to Detect Bacterial Infection in Febrile Infants.
abstract: OBJECTIVE
  The aim of this study was to analyze the usefulness of physical examination, C-reactive protein (CRP), procalcitonin (PCT), white blood cell (WBC) count, and absolute neutrophils counts (ANCs) for the diagnosis of invasive bacterial infections (IBIs) and potentially serious bacterial infections in infants younger than the age of 3 months presenting with fever without source (FWS) to the emergency department (ED).
  
  
  METHODS
  A descriptive retrospective study that includes all infants aged younger than 3 months who presented with FWS to the ED between July 2008 and January 2012. We evaluated diagnostic performance for each test by receiver operating characteristic curve analysis. Sensitivity, specificity, positive likelihood ratio, and negative likelihood ratio were also calculated.
  
  
  RESULTS
  Three hundred eighteen patients met the inclusion criteria. Eleven bacteremia (3.5%) and 76 urinary tract infections (23.9%) were diagnosed. To detect IBI, the areas under the curve for the different tests were as follows: PCT, 0.77 (95% confidence interval [CI], 0.57-0.96); CRP, 0.54 (95% CI, 0.36-0.73); ANC, 0.53 (95% CI, 0.34-0.71); and WBC, 0.42 (0.24-0.61). To detect potentially serious bacterial infections, the areas under the curve were as follows: PCT, 0.66 (95% CI, 0.59-0.74); CRP, 0.68 (0.60-0.76); ANC, 0.64 (0.56-0.71); and WBC, 0.66 (0.58-0.72).
  
  
  CONCLUSIONS
  Procalcitonin is better than CRP, WBC, and ANC to confirm or dismiss the presence of an IBI in infants aged younger than 3 months presenting with FWS to the ED. However, it could not identify almost 30% of infants with IBI. Most patients diagnosed with IBI (10 of 11) presented abnormal values in at least one of the analytical parameters and/or physical appearance. Four of 5 patients with IBI and well appearing presented abnormal results in at least one of the analytical parameters. Therefore, the development of tools combining different tests including the new biomarkers could increase the reliability of the tests for the diagnosis of IBI in these patients.
authors.affiliation: From the Pediatrics Department, 12 de Octubre University Hospital, Madrid, Spain.
authors.forename: Marta Germán
authors.initials: MG
authors.lastname: Díaz
authors.forename: Rosa Pavo
authors.initials: RP
authors.lastname: García
authors.forename: Daniel Blázquez
authors.initials: DB
authors.lastname: Gamero
authors.forename: M Isabel
authors.initials: MI
authors.lastname: González-Tomé
authors.forename: Pilar Cedena
authors.initials: PC
authors.lastname: Romero
authors.forename: Milagros Marín
authors.initials: MM
authors.lastname: Ferrer
authors.forename: Jesús Ruiz
authors.initials: JR
authors.lastname: Contreras
mesh_terms: D016470:Bacteremia / Q000097:blood / Q000175:diagnosis* / Q000382:microbiology; D015415:Biomarkers / Q000097:blood; D002097:C-Reactive Protein / Q000032:analysis; D002116:Calcitonin / Q000097:blood*; D004636:Emergency Service, Hospital; D005260:Female; D005335:Fever of Unknown Origin / Q000097:blood / Q000382:microbiology*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007958:Leukocyte Count; D008297:Male; D009504:Neutrophils / Q000473:pathology; D012372:ROC Curve; D012189:Retrospective Studies; D014552:Urinary Tract Infections / Q000097:blood / Q000175:diagnosis* / Q000382:microbiology
chemical_list: D015415:Biomarkers; D002116:Calcitonin; D002097:C-Reactive Protein