Development and validation of a new questionnaire appropriate to assess respiratory symptoms in current and former smokers without chronic obstructive pulmonary disease: The Respiratory Symptom Questionnaire (RSQ) (Preprint)

BACKGROUND Smokers who stop smoking, including those who do so by switching completely to electronic nicotine delivery systems (ENDS), may experience reductions in respiratory symptoms (e.g., cough). Existing respiratory symptom questionnaires may not be suitable for studying these changes, as they are intended for patient populations, such as those with chronic obstructive pulmonary disease (COPD). OBJECTIVE This study aimed to develop a respiratory symptom questionnaire appropriate for current and former smokers including those without COPD. METHODS The respiratory symptom questionnaire (RSQ) was derived from existing instruments and subject matter expert input and refined through cognitive debriefing interviews (n=49). Next, the RSQ was administered to Smokers (n=202), Switchers (n=208, smokers who switched to ENDS for 6+ months), and Former Smokers (no tobacco use in 6+ months; n=200) for purposes of the quantitative psychometric evaluation. RESULTS The RSQ was evaluated within the context of the graded response model (GRM). GRM assumptions of ordinality of response categories and unidimensionality were met. Test-retest reliability was good, and results provided support for convergent validity. Smokers’ RSQ scores were significantly higher than Former Smokers’ scores (P<.001). Switchers’ RSQ scores were significantly lower than Smokers’ scores (P<.001), and no different from Former Smokers’ (P=.34). CONCLUSIONS The RSQ fills an important gap in the existing toolkit of respiratory symptom questionnaires; it is a reliable and valid tool to assess respiratory symptoms in adult current and former smokers, including those without COPD. Findings also suggest that switching from cigarettes to ENDS may improve respiratory health.