Development and validation of the Cancer Knowledge Scale for the general population: An item response theory approach.

Objective: To develop and validate a new measure of cancer knowledge for members of the general population who have never been diagnosed with cancer.

Methods: Initially, 20 items were generated to measure cancer knowledge. After expert refinement and cognitive interviews, 11 items remained and were completed by 1,076 adults with no history of cancer. Responses were assessed using an item response theory (IRT) approach and differential item functioning.

Results: Items were analyzed using a two-parameter logistic IRT model. Two items with tetrachoric correlation coefficients>0.8 and one item with a discrimination parameter>2.0 were excluded. The final eight items demonstrated a good range of discrimination (1.13 to 1.86) and difficulty (-1.11 to 0.85). No meaningful differential item functioning by participant attributes was detected for these eight items.

Conclusion: The Cancer Knowledge Scale appears to be a reliable and valid measure for the general population.

Practice Implications: The eight-item scale could be used to assess the effects of psychoeducational programs, including those on cancer knowledge, for members of the general population with no cancer history.