OBJECTIVES: Achieving healthcare quality improvements and cost reduction necessitates the participation of activated and informed consumers and patients. Identifying factors leading to low patient activation could help optimize interventions to increase the quality of healthcare. This study attempted to identify predictors of low patient activation measures (PAMs) among patients initiating C1 esterase inhibitor (recombinant) (C1-INH) for the treatment of hereditary angioedema. METHODS: A prospective study administering a self-reported PAM survey to patients initiating C1-INH for the treatment of hereditary angioedema was conducted. Patient age, gender, treating physician specialty, region, and payer type were collected and evaluated as potential predictors of PAM levels. Patients were grouped into 3 mutually exclusive cohorts: low patient activation ≤2, moderate patient activation =3, and high patient activation =4. Due to the rare nature of hereditary angioedema, standardized differences between available factors across PAM level cohorts were computed using PAM level 4 as the reference cohort. RESULTS: There were 94 patients included in the analysis, with the majority being female (74.5%), having a mean age of 40 years, and being from the southern region (40.4%) privately insured (61.7%). The majority of patients were in PAM level 4 (58.5%) followed by PAM level 3 (30.9%) and PAM level ≤2 (10.6 %). Compared to patients in PAM level 4, patients in PAM level ≤2 were more likely to be younger (35.7 vs 38.9; standardized difference [SD]=20.2); however, patients in PAM level 3 were older compared to patients in PAM level 4 (43.7; SD=29.4). Patients in PAM level 3 also had the highest proportion of females compared to patients in PAM level ≤2 (79.3% vs 60%; SD=41.3). CONCLUSIONS: Younger age and being male were associated with the lowest level of patient activation when initiating C1-INH for the treatment of hereditary angioedema.