Evaluation of a respiratory symptom diary for clinical studies of idiopathic pulmonary fibrosis

Background There are no validated patient diaries for evaluating respiratory symptoms in idiopathic pulmonary fibrosis (IPF). Purpose To evaluate the performance properties of the chronic obstructive pulmonary disease (COPD) Evaluating Respiratory Symptoms™ (E-RS™: COPD) measure in patients with IPF. Methods Concept elicitation and cognitive interviews were conducted with IPF patients to evaluate content validity, including comprehensiveness, relevance, and interpretability of E-RS™ items in this patient population. Secondary analyses of IPF clinical study data were performed to evaluate the scoring structure of the tool. With modifications, reliability, validity, and responsiveness of the instrument (E-RS™: IPF) were evaluated. Results Qualitative interviews (n = 30) were conducted. During the elicitation interviews (n = 20), concept saturation for IPF respiratory symptoms was achieved; all respiratory symptoms covered by the E-RS™ were endorsed by ≥ 30% of the sample. During cognitive interviews (n = 10), all participants found the items interpretable and relevant. Factor analyses conducted via secondary analysis of IPF clinical study data identified no total score and four symptom scales: Chest, Breathlessness, Cough, and Sputum. Reliability of each scale was high (internal consistency [α] >0.85); 2-day reproducibility (ICC >0.88). Validity was supported through significant (P < 0.0001) relationships with the St. George's Respiratory Questionnaire (SGRQ), the University of California, San Diego Shortness of Breath Questionnaire (UCSD-SOBQ), and other variables. The scales were responsive to change when evaluated using SGRQ Symptoms, UCSD-SOBQ, and Patient Global Impression of Change as anchors (P < 0.01 to P < 0.0001). Conclusion The E-RS™: IPF is a valid, reliable, and responsive tool for evaluating respiratory symptoms in patients with IPF.