Negative affectivity and social inhibition in cardiovascular disease: evaluating type-D personality and its assessment using item response theory.

OBJECTIVE Individuals with increased levels of both negative affectivity (NA) and social inhibition (SI)-referred to as type-D personality-are at increased risk of adverse cardiac events. We used item response theory (IRT) to evaluate NA, SI, and type-D personality as measured by the DS14. The objectives of this study were (a) to evaluate the relative contribution of individual items to the measurement precision at the cutoff to distinguish type-D from non-type-D personality and (b) to investigate the comparability of NA, SI, and type-D constructs across the general population and clinical populations. METHODS Data from representative samples including 1316 respondents from the general population, 427 respondents diagnosed with coronary heart disease, and 732 persons suffering from hypertension were analyzed using the graded response IRT model. RESULTS In Study 1, the information functions obtained in the IRT analysis showed that (a) all items had highest measurement precision around the cutoff and (b) items are most informative at the higher end of the scale. In Study 2, the IRT analysis showed that measurements were fairly comparable across the general population and clinical populations. CONCLUSIONS The DS14 adequately measures NA and SI, with highest reliability in the trait range around the cutoff. The DS14 is a valid instrument to assess and compare type-D personality across clinical groups.