Agreement between three reference equations for spirometry in adults from a population-based sample

Background: We aimed to compare predicted FEV1 and FEV1/FVC, using three sets of reference equations and to determine their agreement in the classification of normal versus obstruction using a fixed cut-off value. Methods: From the participants of the population-based observational study ICAR - Control and Burden of Asthma and Rhinitis (clinical trials.gov [NCT01771120][1]), we analyzed a random sample of healthy adults (n=146) and of individuals with asthma and/or rhinitis (n=293). Subjects performed spirometry according to ATS/ERS guidelines; they were classified as having normal function or obstruction (defined as a FEV1 < 80% & FEV1/FVC < 70%), using the prediction equations of Global Lung Initiative (GLI) 2012, Hankinson 1999 and European Coal and Steel Community (ECSC) 1993. Agreement between classifications was evaluated. Results: We included 439 individuals (62% females), with a mean (min-max) age of 42.9 (18 - 89) years.Correlation was highest when comparing GLI to Hankinson (r = 0.994). Agreement in FEV1 and FEV1/FVC classification was lower when using the reference equations by ECSC, when compared with the ones by GLI and by Hankinson. In adults younger than 20 years, ECSC has the highest mean (3.87; p < 0.001). In 35 subjects (8%) aged 21-50 years, ECSC prediction was within normal range while with Hankinson and GLI was classified as obstruction. Conclusion: Agreement between GLI and Hankinson prediction equations was highest in this population. Individuals with obstruction may be misclassified as normal by ECSC, especially in the 21 to 50 age group. [1]: /lookup/external-ref?link_type=CLINTRIALGOV&access_num=NCT01771120&atom=%2Ferj%2F44%2FSuppl_58%2F219.atom