Psychometric study of the SF-36v2 in hereditary angioedema due to C1 inhibitor deficiency (C1-INH-HAE)

Abstract

Abstract Background The generic 36-item Short-Form Health Survey (SF-36v2) has been used to assess health related quality of life in adult patients with hereditary angioedema due to C1-inhibitor deficiency (C1-INH-HAE) even though it has not yet been validated for use in this specific disease. Objective This study aims to validate the SF-36v2 for use in adult patients with C1-INH-HAE. Results There was a very low item non-response rate (1–3.4%), with a high ceiling effect in 25/35 items and a low floor effect in 3/35 items. A moderate ceiling effect was observed in 5/8 dimensions of the SF-36v2, whereas no floor effect was noticed in any of the dimensions. Internal consistency was good to excellent with Cronbach's alpha coefficient ranging between 0.82 and 0.93 for the different dimensions. Construct validity was good: seven out of the 8 hypotheses defined on clinical criteria were confirmed, discriminant validity assessment showed significant differences among patients with different C1-INH-HAE severity, convergent validity showed a good correlation among the physical and mental component summaries of the SF-36v2 and the HAE-QoL total score (0.45 and 0.64 respectively, P < 0.001). Test–retest reliability was high with intraclass correlation coefficient varying from 0.758 to 0.962. The minimal clinically important difference was calculated by distribution methods and small differences in the domain scores and in the component summaries scores were shown to be meaningful.  Conclusions The psychometric properties of the SF-36v2 show it can be a useful tool to assess HRQoL in adult patients with C1-INH-HAE, although with some content validity limitation. Methods The psychometric properties of the SF-36v2 were evaluated in an international setting based on responses from 290 adult C1-INH-HAE patients in 11 countries.