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HAE-AS: A Specific Disease Activity Scale for Hereditary Angioedema With C1-Inhibitor Deficiency

Forjaz MJ1*, Ayala A1*, Caminoa M3, Prior N4, Pérez-Fernández E5, Caballero T2,6,7 on behalf of the DV-HAE-QoL Study Group

1National School of Public Health, Institute of Health Carlos III and REDISSEC, Madrid, Spain
2Allergy Department, Hospital Universitario La Paz, Madrid, Spain
3Clinica Marazuela, Talavera de la Reina, Toledo, Spain
4Hospital Universitario Severo Ochoa, Leganés, Madrid, Spain
5Research Unit, Hospital Universitario Fundación Alcorcón, Madrid, Spain
6Hospital La Paz Institute for Health Research (IdiPaz), Madrid, Spain
7Biomedical Research Network on Rare Diseases (CIBERER, U754), Madrid, Spain
*Both authors should be considered joint first authors.

J Investig Allergol Clin Immunol 2021; Vol 31(3) : 246-252
doi: 10.18176/jiaci.0479

Background: The activity of hereditary angioedema due to C1-inhibitor deficiency (C1-INH-HAE) varies between patients and within individual patients.
Objective: This study aims to develop a disease activity scale for C1-INH-HAE (HAE-AS) with sound measurement properties.
Methods: Eleven countries participated in a prospective multicenter cohort study. A clinical questionnaire was self-completed by 290 adult patients with C1-INH-HAE. Patients also completed 2 quality of life scales, the SF-36v2 and the HAE-QoL. Rasch analysis and classic psychometric methods were used to preselect a series of clinical items: number of attacks by location and number of treated attacks, emergency room visits, psychological/psychiatric treatment, missed school/workdays in the previous 6 months; general health; and impairment in everyday work/activities due to pain.
Results: The mean (SD) age was 41.5 (14.7; range, 18-84) years, and 69% were females. The final 12-item Rasch model showed that the HAE-AS had satisfactory reliability (person separation index, 0.748), local item independence, unidimensionality, and no item bias by age or sex. The HAE-AS provided scores in a linear measure, with a mean of 10.66 (3.92; range, 0-30). Further analysis with classic psychometric methods indicated that the HAE-AS linear measure presented moderate-to-high convergent validity with quality of life scales (SF-36v2: physical component, r=–0.33; mental component, 0.555; HAE-QoL, –0.61), and good discriminative validity by age, sex, and disease severity (P<.05).
Conclusions: The HAE-AS is a short, valid, reliable, and psychometrically sound measure of the activity of C1-INH-HAE that could prove useful for research studies.

Key words: C1-INH-HAE, Clinical activity, Hereditary angioedema, Psychometric properties, Rasch analysis

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