Development, validation, and initial results of the Angioedema Activity Score

Background Recurrent angioedema (RecA) is a frequent clinical problem characterized by suddenly occurring cutaneous and/or mucosal swellings. Depending on their location, RecA may be painful, hindering, disfiguring, or even life‐threatening. The assessment of disease activity in affected patients is important to guide treatment decisions. Currently, however, there is no standardized and validated outcome measure available to do so. Objective To develop and validate the first specific patient‐reported outcome instrument to assess disease activity in RecA patients, the Angioedema Activity Score (AAS). Methods After a set of potential AAS items was developed, item evaluation and reduction were performed by means of impact analysis, factor analysis, regression analysis, and by checking for face validity. In addition, the items of the final AAS questionnaire were tested for their validity and reliability during a 12‐week validation study. Results In total, data from 110 and 80 RecA patients were used during the AAS item evaluation and validation phase, respectively. The resulting AAS consisted of five items and was found to have a one‐dimensional structure and excellent internal consistency. It correlated well with other measures of disease activity and quality‐of‐life impairment, thus demonstrating its convergent validity. In addition, the known‐groups validity and test–retest reliability of the AAS were found to be good. Conclusions The AAS is the first validated and reliable tool to determine disease activity in RecA patients, and it may serve as a valuable instrument in future clinical studies and routine patient care.