Type D Assessment in Patients With Chronic Heart Failure and Peripheral Arterial Disease: Evaluation of the Experimental DS⁽³⁾ Scale Using Item Response Theory

Abstract

Type D personality refers to a clustering of 2 stable personality traits, namely negative affectivity and social inhibition. Currently Type D is standardly assessed using the DS14. An experimental Type D personality scale, the DS⁽³⁾, was developed to examine an avenue for assessing Type D more efficiently. The DS⁽³⁾ differs from the DS14 in its use of a 3-point Likert scale to rate responses, use of all negatively worded items, and a rearranged presentation of items. This article examines the psychometric properties of this questionnaire by examining its dimensionality, item and scale properties, and cutoff scores to screen for Type D personality. Data from 2 clinical samples were analyzed using item response theory. The results suggest that the DS⁽³⁾ is a potentially suitable instrument for Type D assessment. It has high reliability, and Type D personality classification based on this scale corresponds well with the current standard Type D assessment based on the DS14.

Notes

Detailed results were as follows: For the SI: t test for means, t(474) = –0.848, p = .397; Levene's F = 0.014, p = .906. For the SI⁽³⁾: t(474) = –0.613, p = .540; Levene's F = 0.907, p = .341. For NA: t(476) = .647, p = .518; Levene's F = .172, p = .678. For NA⁽³⁾: t(476) = –0.843, p = .400; Levene's F = 1.344, p = .247.

To identify the latent scale θ, we fixed the mean and SD of θ scales to 0 and 1 for the sample of PAD patients, respectively. Identification was needed because θ scales are interval-level scales for which a zero-point and unit have to be specified (Embretson & Reise, 2000). For the CHD population, the mean of the θ distribution was estimated from the data and the SD is fixed to 1.