Beyond asthma control: the Composite Asthma Severity Index (CASI)

Published Online: January 13, 2012

As asthma symptoms are reduced, asthma control measurements become ineffective, whereas the Composite Asthma Severity Index (CASI) continues to discriminate level of severity. Awareness of asthma severity is important for treatment decisions, patient characterization, and population studies. The Expert Panel Report three asthma guidelines specify that assessment of disease severity after treatment has begun must include both impairment and risk domains in addition to the treatment required by the individual to achieve that state of overall control. While there are many instruments to measure asthma control, surprisingly there was no instrument available to measure and assess the multidimensional nature of asthma severity until now.

In an article published in The Journal of Allergy & Clinical Immunology (JACI), Wildfire et al present the development and validation of a new multidimensional asthma severity measure. The CASI was developed using data from nearly 1,000 inner-city children and adolescents, and clinical expertise from investigators associated with the National Institutes of Health–supported Inner City Asthma Consortium (ICAC). First, independent aspects of asthma were identified using data from 546 participants in the Asthma Control Evaluation study. Then, 26 ICAC asthma experts made individual and group decisions as to how the components of these domains should be weighted and combined into a final CASI score. Finally, the scale properties of the CASI were evaluated and external validation was conducted using 419 participants from Inner City Anti-IgE Therapy for Asthma (ICATA) trial.

CASI includes five domains: day symptoms and albuterol use, night symptoms and albuterol use, controller treatment, lung function measures, and exacerbations. In external validation, CASI detected a 32% larger improvement between groups than symptoms alone. CASI retained its discriminatory ability even with low levels of symptoms reported after months of guidelines-directed care.

By incorporating symptoms, exacerbations, lung function and treatment requirements into a single index, the CASI combines domains of impairment and future risk with the level of treatment needed to reach the current clinical state, and in doing so, addresses the need for a comprehensive asthma index that reflects disease severity. This measure of asthma severity provides a means to discriminate among individuals who would otherwise appear well controlled and equally severe. Instruments such as CASI which go beyond simply measuring control are necessary to assess the effectiveness of an intervention or drug in the context of guidelines-based care.


The Journal of Allergy and Clinical Immunology (JACI) is the official scientific journal of the AAAAI, and is the most-cited journal in the field of allergy and clinical immunology.

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