Development and validation of the RAND asthma control measure

Abstract

Patient-based measures for asthma control are important in assessing the worldwide impact of this highly prevalent chronic illness. We sought to refine an asthma symptom scale that RAND had previously developed to shorten it and validate it further, as well as reflect updated international expert definitions of asthma control. We conducted rigorous psychometric testing of new and adapted self- Administered survey items in a sample of 2032 adults with asthma. The reliability and preliminary validity of the resulting measure, henceforth referred to as the RAND Asthma Control Measure (RAND-ACM), matched or exceeded that of the original RAND measure and others in the literature. RAND-ACM scores for worse asthma control were significantly associated with worse asthma-related quality of life, increased asthma-related healthcare use, Hispanic ethnicity and lower educational level. Evidence for internal consistency was strong with a Cronbach's a of 0.84. We also found adequate concordance between the RAND-ACM and the Global Initiative for Asthma categories of "uncontrolled", "partly controlled" and "controlled" asthma. The RAND-ACM, a five-item self-reported asthma control survey measure, performs well in a large ethnically-diverse sample of US adults with asthma and provides a cost-free alternative to other asthma control measures currently available.