Study objectives: Health-related quality of life associated with interstitial lung disease has received little attention in clinical studies because there have been no validated methods for directly measuring it. We have assessed the validity of several generic and respiratory-specific quality-of-life instruments in patients with interstitial lung disease.
Design: Cross-sectional study.
Setting: Outpatient pulmonary clinic at a university referral center.
Patients: Fifty patients with interstitial disease such as idiopathic pulmonary fibrosis, sarcoidosis, hypersensitivity pneumonitis, and asbestosis.
Interventions: Patients were administered four quality-of-life questionnaires, the Medical Outcomes Study Short Form 36 (SF-36), the Quality of Well-being scale (QWB), the Chronic Respiratory Questionnaire (CRQ), and the St. George's Respiratory Questionnaire (SGRQ). Patients concomitantly underwent pulmonary function testing and performed a 6-min walk.
Measurements and results: Validation of these instruments was based on testing an a priori hypothesis that worse quality-of-life scores should correlate with more severe physiologic impairment demonstrated by pulmonary function tests, exercise tolerance on the 6-min walk, and dyspnea scores. Our patients, on average, had a moderate degree of physiologic impairment and demonstrated moderately decreased quality-of-life scores. Scores from all four quality-of-life questionnaires correlated significantly with 6-min walk distance and dyspnea score. Scores from the SF-36, QWB, and SGRQ showed significant correlation with FVC, FEV(1), and diffusing capacity as well. The SF-36 and SGRQ consistently showed the strongest correlation with physical impairment.
Conclusions: Our findings indicate that preexisting quality-of-life instruments can be applied to patients with interstitial lung disease and suggest that the SF-36 and the SGRQ, in particular, are sensitive tools for assessing quality of life in these patients. Future intervention studies of patients with interstitial lung disease should consider using these measures.