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

BackgroundAngioedema 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.MethodsThis 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).ResultsParticipants 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.