Spirometric variables (FVC and FEV1) and disease-specific and general quality of life (assessed with the use of the St. George's Respiratory Questionnaire [SGRQ]29 and the Medical Outcomes Study 36-Item Short-Form Health Survey [SF-36],30 respectively) were measured at baseline and at 12, 24, and 36 months (and at the final visit if that did not coincide with an annual visit). Scores on the SGRQ range from 0 to 100, with lower scores indicating better functioning and with a minimal clinically important difference of 4 points.29 The SF-36 is a self-administered general health questionnaire that generates scores across eight health dimensions. Scores range from 0 to 100, with higher scores indicating better health on each dimension.30 Clinically important changes in the SF-36 score are increases of 5 to 10 points in specific domains.31