Angioedema due to acquired C1 inhibitor deficiency: patient experience, conceptual disease model, and assessment of patient-reported outcome measures.

BACKGROUND

Angioedema due to acquired C1 inhibitor deficiency (AAE-C1INH) is a rare, serious condition that manifests with recurring and often painful swelling attacks. No approved treatments or validated patient-reported outcome (PRO) measures exist for AAE-C1INH. This study aimed to develop a conceptual model of AAE-C1INH and explored the relevance of adapting PRO measures validated for hereditary angioedema, another bradykinin-mediated disease.

METHODS

This cross-sectional, qualitative study involved semi-structured interviews with 8 adults living with AAE-C1INH. Open-ended questions elicited participants' descriptions of AAE-C1INH manifestations and daily life impacts. Cognitive interviews assessed perceptions of clarity, comprehension, and meaningful levels of change in PRO measures: Patient Global Impression of Change (PGI-C) and Severity (PGI-S) and Patient Global Assessment of Status (PGA-S) and Change (PGA-C).

RESULTS

Participants reported traumatic medical emergencies, misdiagnoses, and evaluations by a variety of healthcare providers. Daily life impact was common (social/family and treatment-related; n=7). Attack areas most frequently reported were abdomen (n=7), face (n=6), and foot/hand (n=5 each). Evaluating PGI-C, 8/8 participants correctly interpreted the scale to assess symptoms at a given time post-treatment vs. at time of treatment for a theoretical AAE-C1INH attack. Four of 8 participants considered "a little better" ≥2 hours post-treatment and 6/6 considered "better" ≥4 hours as meaningful. Most also considered PGI-S and PGA easy to interpret and relevant to their symptoms.

CONCLUSION

Interviews highlighted the impact of AAE-C1INH on participants' lives and overall well-being. Participants' assessments of PRO items have informed the clinical outcome assessment strategy for the first phase 3 clinical trial exclusively in AAE-C1INH.