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

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.

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.

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.

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.