Asthma outcomes: composite scores of asthma control

Current asthma guidelines recommend assessing the level of a patient's asthma control. Consequently, there is increasing use of asthma control as an outcome measure in clinical research studies. Several composite assessment instruments have been developed to measure asthma control.

National Institutes of Health institutes and federal agencies convened an expert group to propose the most appropriate standardized composite score of asthma control instruments to be used in future asthma studies.

We conducted a comprehensive search of PubMed using both the National Library of Medicine's Medical Subject Headings and key terms to identify studies that attempted to develop and/or test composite score instruments for asthma control. We classified instruments as core (required in future studies), supplemental (used according to study aims and standardized), or emerging (requiring validation and standardization). This work was discussed at a National Institutes of Health-organized workshop convened in March 2010 and finalized in September 2011.

We identified 17 composite score instruments with published validation information; all had comparable content. Eight instruments demonstrated responsiveness over time; 3 demonstrated responsiveness to treatment. A minimal clinically important difference has been established for 3 instruments. The instruments have demographic limitations; some are proprietary, and their use could be limited by cost.

Two asthma composite score instruments are sufficiently validated for use in adult populations, but additional research is necessary to validate their use in nonwhite populations. Gaps also exist in validating instruments for pediatric populations.