Minimally important differences and risk levels for the Composite Asthma Severity Index

The Composite Asthma Severity Index (CASI) is a comprehensive severity scale combining multiple facets of asthma severity: impairment, risk, and treatment.1 The CASI score, which was developed as a research tool for intervention studies, ranges from 0 to 20 points, with higher scores indicating higher levels of severity, and includes 5 domains: day symptoms and albuterol use, night symptoms and albuterol use, controller treatment, lung function measures, and exacerbations. This report expands on the introduction of the CASI score in Wildfire et？al1 by determining risk levels, the minimally important difference (MID), and the suggested effect size for the score.