Validation of a respiratory symptom score from the Quality of Life-Bronchiectasis Questionnaire in adults with Mycobacterium avium complex lung disease.

OBJECTIVE: To assess the psychometric properties of a respiratory symptom score from the Quality of Life-Bronchiectasis Questionnaire in adults with Mycobacterium avium complex (MAC) lung disease. METHODS: Structural validity, internal consistency, test-retest reliability, and known-groups validity were assessed using data from the ARISE (NCT04677543) and ENCORE (NCT04677569) phase 3 trials. Convergent validity was assessed using Exacerbations of Chronic Pulmonary Disease Tool (EXACT), EXACT Respiratory Symptoms (E-RS), St. George Respiratory Questionnaire (SGRQ), and Functional Assessment of Chronic Illness Therapy (FACIT) Fatigue Scale. Anchor-based meaningful within-patient change (MWPC) thresholds were estimated using the Patient Global Impression of Severity Respiratory scale. RESULTS: In total, 362 patients were included for cross-sectional (ARISE: 97, ENCORE: 265) and longitudinal (ARISE: 99) validation analyses. Modern psychometric methods supported item relevance and an essentially unidimensional mean score. The respiratory symptom score demonstrated adequate internal consistency (McDonald's omega: 0.86, Cronbach's alpha: 0.81), test-retest reliability (intraclass correlation coefficient: 0.73), convergent validity (EXACT: -0.72, E-RS: -0.72, SGRQ: -0.77, FACIT-Fatigue: 0.51), and known-groups validity. The estimated MWPC threshold was a 16.67-point median change from baseline (95% CI: 8.33-16.83 points). CONCLUSIONS: The respiratory symptom score is a robust, sensitive, and responsive measure of respiratory symptoms in adults with a new or recurrent MAC lung disease diagnosis.