Validation of the Bronchiectasis Impact Measure (BIM) - a novel patient reported outcome measure

Introduction: Existing quality-of-life and symptom tools used in bronchiectasis trials are either not disease specific or are complex and have not been consistently responsive. We developed a simple patient-reported visual analogue outcome measure, the Bronchiectasis Impact Measure (BIM), for use in clinical research, including clinical trials.

Methods: Patients with bronchiectasis attending a tertiary referral clinic in the east of Scotland were invited to complete the BIM questionnaire and the quality-of-life bronchiectasis questionnaire at baseline with repeat questionnaires after 2 weeks and 6 months. We assessed internal consistency, test–retest reliability, construct validity and responsiveness by evaluating change during an acute exacerbation.

Results: 173 patients were included. The eight domains (cough, sputum, breathlessness, tiredness, activity, general health, control, exacerbations) showed excellent internal consistency (Cronbach’s α 0.93). The intraclass correlation coefficient demonstrated excellent reliability over a 2-week period: cough (0.79, 95% CI 0.70–0.85), sputum (0.86, 95% CI 0.80–0.90), dyspnoea (0.82, 95% CI 0.74–0.87), tiredness (0.88, 95% CI 0.82–0.91), activity (0.84, 95% CI 0.77–0.89), general health (0.81, 95% CI 0.74–0.87), control (0.83, 95% CI 0.75–0.88) and exacerbation (0.71, 95% CI 0.60–0.79). Domains correlated strongly with bronchiectasis severity and exacerbation history. Both distribution and patient-based methods estimated the minimal clinically important difference for each domain as 1.5 points on a 10-point scale. Statistically significant changes in all BIM domains were observed during an acute exacerbation.

Conclusion: The BIM is a simple patient-reported outcome. This study validates the internal consistency, reliability, construct validity and response of the tool at acute exacerbation. Further validation of the tool is now required.