title: International classification of diseases codes showed modest sensitivity for detecting community-acquired pneumonia.
abstract: OBJECTIVE
  To estimate the sensitivity of International Classification of Diseases (ICD-9-CM) coding for detecting hospitalized community-acquired pneumonia and to assess possible determinants for misclassification.
  
  
  METHODS
  Based on microbiological analysis data, 293 patients with a principal diagnosis of community-acquired pneumonia at seven hospitals in the Netherlands were assigned to three categories (pneumococcal pneumonia, pneumonia with other organism, or pneumonia with no organism specified). For these patients, the assigned principal and secondary ICD-9-CM codes in the hospital discharge record were retrieved and the corresponding sensitivity was calculated. Furthermore, pneumonia-related patient characteristics were compared between correctly and incorrectly coded subjects.
  
  
  RESULTS
  The overall sensitivity was 72.4% for the principal code and 79.5% for combined principal and secondary codes. For pneumococcal pneumonia (ICD-9-CM code 481) and pneumonia with specified organism (ICD-9-CM code 482-483), the sensitivities were 35% and 18.3%, respectively. Patient characteristics were not significantly different between correctly and incorrectly coded subjects except for duration of hospital stay, which correlated negatively with coding sensitivity (P=0.01).
  
  
  CONCLUSIONS
  ICD-9-CM codes showed modest sensitivity for detecting community-acquired pneumonia in hospital administrative databases, leaving at least one quarter of pneumonia cases undetected. Sensitivity decreased with longer duration of hospital stay.
authors.affiliation: Division of Pharmacoepidemiology and Pharmacotherapy, Utrecht Institute for Pharmaceutical Sciences, Faculty of Science, Utrecht University, PO Box 80082, 3506 TB Utrecht, The Netherlands.
authors.forename: Ewoudt M W
authors.initials: EM
authors.lastname: van de Garde
authors.forename: Jan Jelrik
authors.initials: JJ
authors.lastname: Oosterheert
authors.forename: Marc
authors.initials: M
authors.lastname: Bonten
authors.forename: Robert C
authors.initials: RC
authors.lastname: Kaplan
authors.forename: Hubert G M
authors.initials: HG
authors.lastname: Leufkens
mesh_terms: D000368:Aged; D017714:Community-Acquired Infections / Q000145:classification / Q000175:diagnosis; D016208:Databases, Factual; D005260:Female; D006760:Hospitalization; D006801:Humans; D038801:International Classification of Diseases; D007902:Length of Stay; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D009426:Netherlands; D011014:Pneumonia / Q000145:classification / Q000175:diagnosis; D011018:Pneumonia, Pneumococcal / Q000145:classification* / Q000175:diagnosis; D016032:Randomized Controlled Trials as Topic; D012680:Sensitivity and Specificity; D013296:Streptococcus pneumoniae