title: Factors associated with misdiagnosis of COPD in  primary care.
abstract: OBJECTIVE
  To assess the misclassification of chronic obstructive pulmonary disease (COPD) in Australian primary care.
  
  
  METHODS
  A cross-sectional study was performed in 31 (19%) practices in one Australian state. 341 patients with COPD (database  diagnosis or current use of tiotropium plus GP confirmation) completed spirometry and questionnaires. Predictors of misclassification were  investigated with multi-level mixed-effects logistic regression allowing for clustering by practice.
  
  
  RESULTS
  Spirometric confirmation of COPD (forced expiratory volume in 1 s/forced vital capacity (FEV1/FVC) ratio <0.7) was not present in  107 (31%) patients; 60 (56%) had normal lung function, seven (7%) had scalloped flow-volume curves and FEV1 <80% predicted, 40  (37%) had restriction (FVC <80% predicted). Among 107 misclassified patients the bronchodilators used were tiotropium in 26% and  long-acting β2-agonists in 22%. The likelihood of misclassification increased with overweight/obesity (odds ratio (OR) 2.66; 95% CI 1.50  to 4.70) and self-reported allergic rhinitis/hay fever (OR 1.72; 95% CI 1.13 to 2.64) after adjustment for age, gender, and smoking.
  
  
  CONCLUSIONS
  Symptom-based diagnosis of COPD in primary care is unreliable, especially if patients are overweight, so diagnostic  spirometry is essential to avoid inappropriate management.
authors.affiliation: Menzies Research Institute, University of Tasmania, Tasmania, Australia. Julia.Walters@utas.edu.au
authors.forename: Julia A
authors.initials: JA
authors.lastname: Walters
authors.forename: E Haydn
authors.initials: EH
authors.lastname: Walters
authors.forename: Mark
authors.initials: M
authors.lastname: Nelson
authors.forename: Andrew
authors.initials: A
authors.lastname: Robinson
authors.forename: Jenn
authors.initials: J
authors.lastname: Scott
authors.forename: Paul
authors.initials: P
authors.lastname: Turner
authors.forename: Richard
authors.initials: R
authors.lastname: Wood-Baker
mesh_terms: D001993:Bronchodilator Agents / Q000627:therapeutic use; D003430:Cross-Sectional Studies; D003951:Diagnostic Errors / Q000706:statistics & numerical data*; D005541:Forced Expiratory Volume; D006801:Humans; D016015:Logistic Models; D011320:Primary Health Care; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis* / Q000188:drug therapy / Q000453:epidemiology*; D012602:Scopolamine Derivatives / Q000627:therapeutic use; D012720:Severity of Illness Index; D013147:Spirometry / Q000706:statistics & numerical data; D011795:Surveys and Questionnaires; D013648:Tasmania / Q000453:epidemiology; D000069447:Tiotropium Bromide
chemical_list: D001993:Bronchodilator Agents; D012602:Scopolamine Derivatives; D000069447:Tiotropium Bromide