Development and validation of a US quality of life instrument for hereditary angioedema due to C1 inhibitor deficiency
Anthony J. Castaldo, Nikolaj Siersbæk, Deborah Corcoran, Christine N. Selva, Christian Jervelund, Sandra C. Christiansen, Marc A. Riedl, Bruce L. Zuraw, Paula J. Busse
Abstract
BACKGROUND: Hereditary angioedema (HAE) attacks are unpredictable, cause a substantial and enduring burden of illness, and are potentially fatal. Because of issues unique to the US health care system, there is a need for a US-validated, HAE-specific quality of life (QoL) instrument. OBJECTIVE: To develop and validate a US HAE-specific QoL instrument according to US Food and Drug Administration guidelines and established methodologies. METHODS: We generated 41 QoL-related items likely relevant to US patients with HAE due to C1 inhibitor (C1INH) deficiency (HAE-C1INH) and performed a 10-patient pilot study to refine the question wording. A total of 415 US patients with HAE-C1INH completed the initial 41-item instrument online, thereby providing data for item reduction, factor analysis, and the assessment of validity and reliability. We used a multiple linear regression to identify the drivers of the total and domain scores. Convergent validity analysis was used to assess the extent to which the HAE-C1INH QoL instrument (HAE-C1INH-QoL) is theoretically related to the angioedema-QoL instrument (AE-QoL). RESULTS: Item reduction and factor analysis yielded a final instrument of 31 items across 5 domains, and the assessment analysis showed that the HAE-C1INH-QoL is valid and reliable. Attack frequency and severity were statistically significant factors that influenced the total and domain scores. Correlation analysis of the 2 instruments indicated that 8 items of the HAE-C1INH-QoL were not included or well-described in the AE-QoL. CONCLUSION: The HAE-C1INH-QoL is the first HAE-specific QoL tool validated in the United States. When compared with the AE-QoL, the items in our instrument are more relevant to US patients with HAE.