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

Rationale: The Bronchiectasis Health Questionnaire (BHQ) is a concise, self-administered and disease-specific instrument for measuring health-related quality-of-life (HRQoL) in bronchiectasis.

Objectives: To investigate the psychometric properties of 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, along with a cross-sectional observational cohort including 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 BHQ scores and the Quality of Life - Bronchiectasis Respiratory Symptom Scale (QoL-B-RSS), with correlation coefficient 0.698 in the trial cohort and 0.567 in the clinical cohort (both P<0.0001). Known-groups validity indicated significant differences in BHQ scores stratified by baseline Bronchiectasis Severity Index. BHQ scores correlated modestly with both FEV1% predicted and exacerbation frequency within the previous year. In the trial cohort, BHQ demonstrated excellent internal consistency (Cronbach's alpha: 0.893) and test-retest reliability (intraclass correlation coefficient: 0.853). An 8-point improvement in QoL-B-RSS 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.