Abstract
BACKGROUND: The Living with Pulmonary Fibrosis (L-PF) questionnaire assesses symptoms and quality of life in patients with fibrosing interstitial lung diseases (ILDs). Its Dyspnoea and Cough domains, whose items' responses are based on a 24-hour recall, have scores ranging from 0 to 100, with higher scores indicating greater symptom severity. We evaluated the ability of these domain scores to detect change and estimated their meaningful change thresholds in patients with progressive fibrosing ILDs. METHODS: The INBUILD trial enrolled subjects with progressive fibrosing ILDs other than idiopathic pulmonary fibrosis. The L-PF questionnaire was completed at baseline and week 52. The responsiveness of the Dyspnoea and Cough scores was evaluated by comparing changes in these scores with 52-week changes in three anchors: forced vital capacity % predicted and two self-reported items, one for global physical health and one for global quality of life. We used a triangulation approach including anchor-based and distribution-based methods to estimate meaningful change thresholds. RESULTS: The analyses included 542 subjects with an L-PF Dyspnoea score at baseline and week 52, and 538 subjects with an L-PF Cough score at baseline and week 52. The L-PF Dyspnoea and Cough scores were responsive to change over 52 weeks. Triangulation of anchor-based and distribution-based estimates resulted in meaningful change thresholds of 6 to 7 points for the L-PF Dyspnoea score and 4 to 5 points for the L-PF Cough score to differentiate subjects who were stable or improved from those who deteriorated. CONCLUSION: These analyses support the responsiveness, one aspect of validity, of the L-PF Dyspnoea and Cough domains scores as measures of symptom severity in patients with progressive fibrosing ILDs. Estimates for meaningful change thresholds in these domain scores may be of value in interpreting the effects of interventions in these patients. TRIAL REGISTRATION NUMBER: NCT02999178.