title: Clinical predictors of occult pneumonia in the febrile child.
abstract: BACKGROUND
  The utility of chest radiographs (CXRs) for detecting occult pneumonia (OP) among pediatric patients without lower respiratory tract signs has been previously studied, but no predictors other than white blood cell count (WBC) and height of fever have been investigated.
  
  
  OBJECTIVE
  To identify predictors of OP in pediatric patients in the postconjugate pneumococcal vaccination era.
  
  
  METHODS
  This was a retrospective cross sectional study that was conducted in a large urban pediatric hospital. Physician records of emergency department (ED) patients of age 10 years or less who presented with fever (38 degrees C) and had a CXR obtained for suspected pneumonia were reviewed. Patients were classified into two groups: "signs of pneumonia" and "no signs of pneumonia" on the basis of the presence or absence of respiratory distress, tachypnea, or lower respiratory tract findings. Occult pneumonia was defined as radiographic pneumonia in a patient without signs of pneumonia.
  
  
  RESULTS
  Two thousand one hundred twenty-eight patients were studied. Among patients categorized as having no signs of pneumonia (n = 1,084), 5.3% (95% CI = 4.0% to 6.8%) had OP. Presence of cough and longer duration of cough (greater than 10 days) had positive likelihood ratios (LR+) of 1.24 (95% CI = 1.15 to 1.33) and 2.25 (95% CI = 1.21 to 4.20), respectively. Absence of cough had a negative likelihood ratio (LR-) of 0.19 (95% CI = 0.05 to 0.75). The likelihood of OP increased with increasing duration of fever (LR+ for more than three days and more than five days of fever, respectively: 1.62; 95% CI = 1.13 to 2.31 and 2.24; 95% CI = 1.35 to 3.71). When obtained (56% of patients), WBC was a predictor of OP, with a LR+ of 1.76 (95% CI = 1.40 to 2.22) and 2.17 (95% CI = 1.58 to 2.96) for WBC of >15,000/mm3 and >20,000/mm3, respectively.
  
  
  CONCLUSIONS
  Occult pneumonia was found in 5.3% of patients with fever and no lower respiratory tract findings, tachypnea, or respiratory distress. There is limited utility in obtaining a CXR in febrile children without cough. The likelihood of pneumonia increased with longer duration of cough or fever or in the presence of leukocytosis.
authors.affiliation: Division of Emergency Medicine, Children's Hospital Boston, Harvard Medical School, Boston, MA, USA. charles.murphy@mountsinai.org
authors.forename: Charles G
authors.initials: CG
authors.lastname: Murphy
authors.forename: Alma C
authors.initials: AC
authors.lastname: van de Pol
authors.forename: Marvin B
authors.initials: MB
authors.lastname: Harper
authors.forename: Richard G
authors.initials: RG
authors.lastname: Bachur
mesh_terms: D017677:Age Distribution; D001900:Boston / Q000453:epidemiology; D002675:Child, Preschool; D015897:Comorbidity; D003371:Cough / Q000453:epidemiology; D003430:Cross-Sectional Studies; D003937:Diagnosis, Differential; D005334:Fever / Q000453:epidemiology*; D006801:Humans; D007223:Infant; D016013:Likelihood Functions; D016015:Logistic Models; D008487:Medical History Taking / Q000706:statistics & numerical data; D010808:Physical Examination / Q000706:statistics & numerical data; D018410:Pneumonia, Bacterial / Q000175:diagnosis* / Q000453:epidemiology*; D015995:Prevalence; D012141:Respiratory Tract Infections / Q000175:diagnosis / Q000453:epidemiology; D012189:Retrospective Studies