Psychometric Evaluation of a Cardiac Genetic Knowledge Scale Across Pretest Education Models

Accurate assessment of patient knowledge is an essential component of informed decision-making in cardiac genetic testing. An eight-item cardiac genetic knowledge scale was previously developed to support evaluation of informed choice within the Multidimensional Model of Informed Choice, but its psychometric properties have not been formally assessed. Data were pooled from 318 adults with hypertrophic or dilated cardiomyopathy who received pretest education through a genetics webinar (n = 121), cardiologist-led counseling (n = 61), or a prerecorded educational video (n = 136). Exploratory factor analysis (EFA), confirmatory factor analysis (CFA), and two-parameter logistic item response theory (IRT) modeling were used to evaluate factor structure, item performance, and measurement precision. Mean knowledge scores ranged from 6.2 to 7.1 out of 8, with 62%-91% of participants classified as having adequate knowledge (≥ 75%). EFA supported a two-factor solution reflecting disease-related and testing-related knowledge; however, CFA demonstrated substantial overlap between these domains (r = 0.81), with one- and two-factor models showing comparable fit. Overall, findings supported a dominant general knowledge construct. IRT analyses demonstrated acceptable model fit (M2 = 39.35, df = 20, p = 0.006) and meaningful variability in item performance. Two items showed strong discrimination across the knowledge continuum, while several items contributed less information. All items had negative difficulty parameters, indicating that the scale was primarily targeted toward individuals with below-average knowledge. Test information curves showed greatest measurement precision at low-to-moderate knowledge levels. Raw scores were highly correlated with latent trait estimates (r = 0.97, p < 0.001), supporting the practicality of simple sum-score interpretation. This study provides preliminary evidence supporting the internal structural validity of the eight-item cardiac genetic knowledge scale. The scale demonstrated acceptable item performance in this sample and effectively identified individuals with lower levels of knowledge and specific educational gaps across care models, supporting its potential use as the knowledge component of informed decision-making measures in cardiac genetic testing.