Validation of the CaReQoL asthma: a patient reported outcome measure for monitoring the perceived effects of pulmonary rehabilitation in adult patients with severe refractory asthma

Background: The CaReQoL Asthma assesses the care-related quality of life outcomes of pulmonary rehabilitation retrospectively in patients with severe asthma. The questionnaire comprises five domains (physical functioning; social functioning; coping with asthma; knowledge about asthma; medication).

Aim: To investigate construct and criterion validity of the CaReQoL Asthma, as well as its responsiveness and minimal important change (MIC), in comparison with other health measures (AQLQ, ACQ and FEV₁).

Methods: Eighty three adults with severe refractory asthma filled out the CaReQoL Asthma at 6 and 12 months after a 12-week personalized multidisciplinary pulmonary rehabilitation program in a tertiary asthma centre, either in Switzerland or The Netherlands. Construct validity and responsiveness were assessed by testing pre-defined hypotheses about associations with changes in AQLQ, ACQ and FEV₁ scores. Criterion validity and MIC was assessed using Global Perceived Effect (GPE). Factor analyses, Cronbach's alpha, Spearman's correlations, paired t-tests and Student-Newman-Keuls tests were performed.

Results: Cronbach's alphas of the questionnaire domains ranged from 0.82 to 0.95. Good construct validity and responsiveness were found; 84% of the assessed correlations confirm pre-defined hypotheses and reflect both weak and moderate to strong correlations. Good criterion validity was also identified, with CaReQol scores discriminating better than other health measures between levels of GPE at 6 months post-rehabilitation. The MIC for the total score was estimated at 0.84.

Conclusion: These study results suggest that the CaReQoL Asthma is a valid and responsive instrument and shows to be a comprehensive and tailored questionnaire for evaluating and monitoring outcomes of pulmonary rehabilitation in patients with severe refractory asthma. In order to further substantiate the reliability and validity of the CaReQoL Asthma, as well as to monitor outcomes of pulmonary rehabilitation in patients with severe asthma, it is recommended to use the CaReQoL Asthma in addition to other disease specific instruments.