Use of Item Response Theory to Examine a Cardiovascular Health Knowledge Measure for Adolescents with Elevated Blood Pressure

The purpose of this study was to assess the psychometric properties of a cardiovascular health knowledge measure for adolescents using item response theory. The measure was developed in the context of a cardiovascular lifestyle intervention for adolescents with elevated blood pressure. Sample consisted of 167 adolescents (mean age = 16.2 years) who completed the Cardiovascular Health Knowledge Assessment (CHKA), a 34-item multiple choice test, at baseline and post-intervention. The CHKA was unidimensional and internal consistency was .65 at pretest and .74 at posttest. Rasch analysis results indicated that at pretest the items targeted adolescents with variable levels of health knowledge. However, based on results at posttest, additional hard items are needed to account for the increase in level of cardiovascular health knowledge at post-intervention. Change in knowledge scores was examined using Rasch analysis. Findings indicated there was significant improvement in health knowledge over time [t(119) = -10.3, p < .0001]. In summary, the CHKA appears to contain items that are good approximations of the construct cardiovascular health knowledge and items that target adolescents with moderate levels of knowledge.