Proceedings of The Physiological Society

Future Physiology (Leeds, UK) (2017) Proc Physiol Soc 39, PC55

Poster Communications

Reclassification of bronchodilator reversibility in the U-BIOPRED adult asthma cohort using z scores

A. J. Simpson1, S. J. Fowler1, *. on behalf of the U-BIOPRED Study Group2

1. Division of Infection, Immunity & Respiratory Medicine, University of Manchester, Manchester, United Kingdom. 2. U-BIOPRED, Http://, United Kingdom.

  • Figure. Sankey diagram demonstrating the reclassification of bronchodilator reversibility (BDR) in the U-BIOPRED adult asthma cohort using the ERS/ATS (2005) criteria2 and the z-score criteria proposed by Quanjer et al., (2017)1.

Background: Bronchodilator reversibility (BDR) is a hallmark feature of asthma. Current ERS/ATS guidelines for BDR, i.e., >12% and >200 ml increase in Forced Expiratory Volume in one second (FEV1) and/or Forced Vital Capacity (FVC), leads to a bias in that the likelihood of BDR increases with deteriorating pulmonary function. Consequently, new criteria for BDR based on z scores, which eliminates this artefact, have been proposed: ΔzFEV1 > 0.78 or ΔzFVC > 0.64 (Quanjer, Chest 2017;151:1088). Aim: We applied the newly proposed BDR criteria to the U-BIOPRED adult asthma cohort to; i) determine the influence of these new criteria on the prevalence of BDR and, ii) explore the difference in clinical characteristics between individuals with FEV1 BDR and FVC BDR. Methods: Four-hundred and ninety-nine asthmatics underwent a standard BDR test. Results: Using the ERS/ATS BDR criteria, 55% of the asthma cohort displayed BDR. The re-evaluation of BDR using ΔzFEV1 > 0.78 or ΔzFVC > 0.64, resulted in the reclassification of 12% of the population; 9% no longer having BDR and 3% now fulfilling BDR criteria. A further 10% with BDR changed classification on the type of BDR they displayed (Figure 1). Individuals with FVC BDR only and both FEV1 and FVC BDR had worse lung function, higher BMI and poorer asthma control and quality of life compared to individuals with FEV1 BDR only (P<0.05). Conclusion. The new criteria for the classification of BDR based on z-scores is free from bias produced by baseline lung function values. These new criteria influenced the BDR classification in nearly one quarter of the U-BIOPRED adult asthma cohort. Given that we observed significant differences in clinical characteristics between BDR classifications, our results substantiate the proposal that FVC BDR and FEV1 BDR should be considered independently.

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