Psychometric Validation of the Pulmonary Arterial Hypertension-Symptoms and Impact (PAH-SYMPACT) Questionnaire: Results of the SYMPHONY Trial

Background: Disease-specific patient-reported outcome (PRO) instruments are important in assessing the impact of disease and treatment. The Pulmonary Arterial Hypertension-Symptoms and Impact Questionnaire is the first instrument for quantifying pulmonary arterial hypertension (PAH) symptoms and impacts developed according to the 2009 US Food and Drug Administration PRO guidance; previous qualitative research in patients with PAH supported its initial content validity. Methods: Content finalization and psychometric validation were conducted by using data from A Study of Macitentan in Pulmonary Arterial Hypertension to Validate the PAH-SYMPACT (SYMPHONY), a single-arm, 16-week trial with macitentan 10 mg in US patients with PAH. Item performance, Rasch analysis, and factor analyses were used to select the final item content of the PRO and to define its domain structure. Internal consistency, test-retest reliability, known-group and construct validity, sensitivity to change, and influence of oxygen on item performance were evaluated. Results: Data from 278 patients (79% female; mean age: 60 years) were analyzed. Following removal of redundant/misfitting items, the final questionnaire has 11 symptom items across two domains (cardiopulmonary and cardiovascular symptoms) and 11 impact items across two domains (physical and cognitive/emotional impacts). Differential item function analysis confirmed that PRO scoring is unaffected by oxygen use. For all four domains, internal consistency reliability was high (Cronbach's alpha > 0.80), and scores were highly reproducible in stable patients (intraclass correlation coefficient: 0.84-0.94). Correlations with the Cambridge Pulmonary Hypertension Outcome Review questionnaire and the 36-item Medical Outcomes Study Short Form Survey were moderate to high ([r] = 0.34-0.80). The questionnaire differentiated well between patients with varying disease severity levels and was sensitive to improvements in clinician- and patient-reported disease severity. Conclusions: The Pulmonary Arterial Hypertension-Symptoms and Impact Questionnaire is a brief, disease-specific PRO instrument possessing good psychometric properties that can be administered in clinical practice and clinical studies. Trial Registry: ClinicalTrials.gov; No.: NCT01841762; URL: www.clinicaltrials.gov.