Psychometric Validation and Determination of the Minimal Clinically Important Difference for the Bronchiectasis Health Questionnaire in Adults with Bronchiectasis

Abstract Rationale The Bronchiectasis Health Questionnaire (BHQ) is a concise, self-administered, and disease-specific instrument for measuring health-related quality of life in bronchiectasis. Objectives We sought to investigate the psychometric properties of a simplified Mandarin BHQ and determine the minimum clinically important difference (MCID) as a reliable clinical endpoint for assessing the efficacy of bronchiectasis treatments. Methods A longitudinal, randomized controlled trial cohort of 357 patients treated with tobramycin inhalation solution or saline inhalation for Pseudomonas aeruginosa infection and a cross-sectional observational cohort of 436 patients with bronchiectasis were analyzed. Psychometric analyses encompassed convergent validity, known-groups validity, internal consistency, test–retest reliability, and responsiveness. Both anchor-based and distribution-based approaches were utilized to calculate the MCID for therapeutic response. Results There were significant positive correlations between scores on the BHQ and those on the Quality of Life–Bronchiectasis Respiratory Symptom Scale, with correlation coefficients of 0.698 in the trial cohort and 0.567 in the clinical cohort (both Ps < 0.0001). Known-groups validity indicated significant differences in BHQ scores stratified by baseline Bronchiectasis Severity Index. BHQ scores correlated modestly with both forced expiratory volume in 1 second percent predicted and exacerbation frequency within the previous year. In the trial cohort, the BHQ demonstrated excellent internal consistency (Cronbach’s α = 0.893) and test–retest reliability (intraclass correlation coefficient = 0.853). An 8-point improvement in scores on the Quality of Life–Bronchiectasis Respiratory Symptom Scale corresponded to a mean increase of 5.49 points in BHQ scores after 4-week treatment. The MCID for BHQ was consistently 3 points. Conclusions The BHQ (MCID: 3 points) represents a clinically meaningful tool for evaluating therapeutic intervention outcomes and patient-centered outcomes in patients with bronchiectasis.