title: Can spirometric norms be set using pre- or post- bronchodilator test results in older people?
abstract: BACKGROUND
  Chronic Obstructive Pulmonary Disease (COPD) is defined by post-bronchodilator spirometry. Data on "normal values" come predominantly from pre-bronchodilator spirometry. The effects of this on diagnosis are unknown.
  
  
  METHODS
  Lower limits of normal (LLN) were estimated from "normal" participants in the Burden of Obstructive Lung Disease (BOLD) programme. Values separately derived using pre- and post-bronchodilator spirometry were compared. Sensitivity and specificity of criteria derived from pre-bronchodilator spirometry and pre-bronchodilator spirometry adjusted by a constant were assessed in the remaining population. The "gold standard" was the LLN for the post-bronchodilator spirometry in the "normal population". For FEV1/FVC, sensitivity and specificity of criteria were also assessed when a fixed value of < 70% was used rather than LLN.
  
  
  RESULTS
  Of 6,600 participants with full data, 1,354 were defined as "normal". Mean differences between pre- and post- bronchodilator measurements were small and the Bland-Altman plots showed no association between difference and mean value. Compared with using the gold standard, however, tests using pre-bronchodilator spirometry had a sensitivity and specificity of detecting a low FEV1 of 78.4% and 100%, a low FVC of 99.8% and 99.1% and a low FEV1/FVC ratio of 65% and 100%. Adjusting this by a constant improved the sensitivity without substantially altering the specificity for FEV1 (99%, 99.8%), FVC (97.4%, 99.9%) and FEV1/FVC (98.7%, 99.5%).
  
  
  CONCLUSIONS
  Using pre-bronchodilator spirometry to derive norms for lung function reduces sensitivity compared to a post-bronchodilator gold standard. Adjustment of these values by a constant can improve validity of the test.
authors.affiliation: Respiratory Epidemiology and Public Health, National Heart and Lung Institute, Imperial College, London, UK.
authors.forename: Bernet
authors.initials: B
authors.lastname: Kato
authors.forename: Amund
authors.initials: A
authors.lastname: Gulsvik
authors.forename: William
authors.initials: W
authors.lastname: Vollmer
authors.forename: Christer
authors.initials: C
authors.lastname: Janson
authors.forename: Michael
authors.initials: M
authors.lastname: Studnika
authors.forename: Sonia
authors.initials: S
authors.lastname: Buist
authors.forename: Peter
authors.initials: P
authors.lastname: Burney
mesh_terms: D000367:Age Factors; D000368:Aged; D001993:Bronchodilator Agents; D005060:Europe; D005541:Forced Expiratory Volume; D006801:Humans; D008168:Lung / Q000502:physiology*; D008875:Middle Aged; D011237:Predictive Value of Tests; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis* / Q000503:physiopathology; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013147:Spirometry / Q000592:standards*; D014797:Vital Capacity
chemical_list: D001993:Bronchodilator Agents