title: A cross-sectional study of the identification of prevalent asthma and chronic obstructive pulmonary disease among initiators of long-acting β-agonists in health insurance claims data.
abstract: BACKGROUND
  Claims data are potentially useful for identifying long-acting β-agonist (LABA) use by patients with asthma, a practice that is associated with increased mortality. We evaluated the accuracy of claims data for classifying prevalent asthma and chronic obstructive pulmonary disease (COPD) among initiators of LABAs.
  
  
  METHODS
  This study included adult LABA initiators during 2005-2008 in a US commercial health plan. Diagnosis codes from the 6 months before LABA initiation identified potential asthma or COPD and a physician adjudicated case status using abstracted medical records. We estimated the positive predictive value (PPV) and 95% confidence intervals (CI) of covariate patterns for identifying asthma and COPD.
  
  
  RESULTS
  We sought 520 medical records at random from 225,079 LABA initiators and received 370 (71%). The PPV for at least one asthma claim was 74% (CI 63-82), and decreased as age increased. Having at least one COPD claim resulted in a PPV of 82% (CI 72-89), and of over 90% among older patients, men, and recipients of inhaled anticholinergic drugs. Only 2% (CI 0.2-7.6) of patients with a claim for COPD alone were found to have both COPD and asthma, while 9% (CI 4-16) had asthma only. Twenty-one percent (CI 14-30) of patients with claims for both diagnoses had both conditions. Among patients with no asthma or COPD claims, 62% (CI 50-72) had no confirmed diagnosis and 29% (CI 19-39) had confirmed asthma.
  
  
  CONCLUSIONS
  Subsets of patients with asthma, COPD, and both conditions can be identified and differentiated using claims data, although categorization of the remaining patients is infeasible. Safety surveillance for off-label use of LABAs must account for this limitation.
authors.affiliation: Departments of Health Services, Policy & Practice and Epidemiology, Brown University School of Public Health, Brown University, Box G-121-7, 121 South Main Street, Providence, RI 02903, USA. david_dore@brown.edu.
authors.forename: David D
authors.initials: DD
authors.lastname: Dore
authors.forename: Najat
authors.initials: N
authors.lastname: Ziyadeh
authors.forename: Bin
authors.initials: B
authors.lastname: Cai
authors.forename: C Robin
authors.initials: CR
authors.lastname: Clifford
authors.forename: Heather
authors.initials: H
authors.lastname: Norman
authors.forename: John D
authors.initials: JD
authors.lastname: Seeger
mesh_terms: D058666:Adrenergic beta-2 Receptor Agonists / Q000627:therapeutic use*; D000328:Adult; D001249:Asthma / Q000188:drug therapy*; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007348:Insurance, Health; D008297:Male; D008875:Middle Aged; D056687:Off-Label Use / Q000706:statistics & numerical data*; D029424:Pulmonary Disease, Chronic Obstructive / Q000188:drug therapy*; D055815:Young Adult
chemical_list: D058666:Adrenergic beta-2 Receptor Agonists