Defining Resilience to Smoking Related Lung Disease: A Modified Delphi Approach from SPIROMICS.

Rationale Diagnosis of chronic obstructive pulmonary disease (COPD) relies on abnormal spirometry. However, spirometry may underestimate the effects of smoking, missing smokers with respiratory disease that have minimal or no airflow obstruction. Objectives Develop a multi-dimensional definition of a lung-related "resilient smoker" that is useful in research studies; then identify a resilient smoker subgroup in the SPIROMICS cohort using this definition. Methods We performed a three-round modified Delphi survey among a panel of COPD experts to identify and reach a consensus on clinical and radiographic domains to be included in a lung-related resilient smoker definition. Consensus on domains of resilience was defined as ≥80% of experts voting "agree" or "strongly agree" on a 5-point Likert scale. The Delphi-derived definition of resilience was applied to SPIROMICS to identify resilient smokers, whom we then characterized using known biomarkers of COPD. Results Consensus was achieved on 6 of 12 diagnostic items which include: cough and sputum production, dyspnea, radiographic measures of emphysema and small airways disease, exacerbations, and decline in FEV1. Although 892 SPIROMICS participants were classified as smokers with preserved lung function by spirometry, only 149 participants (16.7%) qualified as resilient smokers by our definition. Blood biomarker expression of C-reactive protein (CRP) and soluble tumor necrosis receptor factor1A (sTNFRSF1A) was lower in resilient than non-resilient smokers (P=0.02 and P=0.03). Conclusions A Delphi-derived consensus definition of resilient smoker identified 83.3% of smokers with preserved spirometry as "non-resilient" based on the presence of adverse effects of smoking on the lung. Resilient smokers were biologically distinct from non-resilient smokers based on CRP measurements. Clinical trial registered with ClinicalTrials.gov (NCT01969344).