As there are an increasing number of medical tests, it is even more important that patients understand the results from diagnostic tests in order to increase their probability of making accurate, informed decisions about their healthcare. The current paper outlines the development of the Knowledge of Diagnostic Test scale (KDT), a new instrument designed to measure the ability to understand the methodology of diagnostic testing and to apply diagnostic test results to accurate informed decision-making. Using Item Response Theory (IRT) in two studies, we investigated items to create an efficient measure of knowledge of diagnostic tests. Results suggested three items had desirable psychometric properties (i.e., of discriminability and difficulty) for measuring an average person’s diagnostic test knowledge. Implications for use in healthcare settings are briefly discussed.
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