Clinimetric properties of outcome measures in bronchiectasis

Rationale: There are a lack of outcome measures with robust clinimetric properties in bronchiectasis. Objective: To determine the clinimetric properties (reliability over one year during clinical stability and responsiveness over a course of antibiotics for pulmonary exacerbation) of objective and patient-reported outcome measures. Methods: This multi-centre cohort study included adults with bronchiectasis from seven UK hospitals. Participants attended four visits, four months apart over one year while clinically stable and at the beginning/end of exacerbation and completed lung function (spirometry and multiple breath washout), provided a blood sample for C-reactive protein measurement and completed health-related quality of life (HRQoL) questionnaires (Quality of Life-Bronchiectasis (QoL-B), St. George’s Respiratory Questionnaire (SGRQ) and EuroQoL (EQ-5D-5L). Results: Participants (n=132) had a mean (SD) age of 66 (11) years, 64% were female. Lung function parameters (forced expiratory volume in one second (FEV₁), lung clearance index (LCI^2.5)) were reliable over time (coefficient of variation (CV):<10%). With regards to responsiveness, FEV₁ demonstrated better properties than LCI, therefore a clear justification for use of LCI in future trials is needed. CRP was less reliable (CV>20%) over time than FEV₁ and LCI^2.5 and whilst CRP had a large mean change between the start and end of an exacerbation, this may have been driven by a small number of patients having a large change in CRP. Reliability of HRQoL questionnaires/ questionnaire domains ranged from acceptable (CV:20-30%) to good (CV:10-20%) and HRQoL were responsive to treatment of exacerbations. Considering the specific questionnaire domain relevant to the intervention and its associated clinimetric properties is important. Additional statistics will support future power/sample-size analysis. Conclusions: This information on the clinimetric properties of lung function parameters, CRP and HRQoL parameters should be used to inform the choice of outcome measures used in future bronchiectasis trials.