Development and testing of the KnowGene scale to assess general cancer genetic knowledge related to multigene panel testing.

Abstract

To develop and evaluate a measure of cancer genetics knowledge relevant to multigene panel testing. The instrument was developed using systematic input from a national panel of genetics experts, acceptability evaluation by patient advocates, and cognitive testing. Twenty-four candidate items were completed by 591 breast or gynecological patients who had undergone genetic counseling and multigene panel testing in the past 18 months. A unidimensional item response theory model was fit with a mix of 2-parameter logistic nested response (2 plnrm) and 2-parameter logistic (2 pl) items. Key domains addressing cancer genetics knowledge were found to be overlapping. Of the 24 candidate items, 8 items were removed due to poor discrimination or local dependence. The remaining 16 items had good fit (RMSEA = 0.045, CFI = 0.946) and discrimination parameters ranging from 0.49 to 1.60. The items specified as 2 plnrm distinguish between those answering incorrect versus don't know, with discrimination ranging from 0.51 to 1.02. Information curves were highest among those with lower knowledge. KnowGene is a rigorously developed and effective measure of knowledge after cancer genetic counseling and multigene panel testing. Measuring knowledge in a systematic way will inform practice and research initiatives in cancer genetics.