RESPONSIVENESS OF A BRIEF MEASURE OF SMOKERS' KNOWLEDGE OF LUNG CANCER SCREENING WITH LOW-DOSE COMPUTED TOMOGRAPHY
Method: Responsiveness of a measure refers to its ability to detect change. A previous psychometric analysis of a 12-item knowledge measure showed good test-retest reliability (ICC=.84) and good discrimination between high and low performers, although item difficulty was high for several items. In this study we examined the responsiveness of the total scores and individual items to detect change in knowledge as a result of viewing a video-based decision aid. We sent a REDCap survey link to smokers that agreed to participate in research studies. Eligible smokers were aged 55 to 80 years, current smokers or had quit within the last 15 years, and fluent in English. They completed a baseline survey, viewed a video-based decision aid about lung cancer screening, and completed a follow-up survey. The analysis used a paired samples t-test for the full measure, and individual items were examined.
Result: The smokers (N=30) were primarily White (63%), had less than a college degree (63%), and half were female (50%). They had a mean age of 61.5 years (standard deviation [SD]=4.7) and had smoked for an average of 36.9 years (SD=16.7). Knowledge scores improved significantly from the baseline to follow-up survey (paired samples t-test=7.57, P<.001). The mean difference score for the 12-item measure was 3.97 (SD=2.87, 95% CI=2.90-5.04).
Several items were less responsive than others. No smokers selected all the correct responses on the screening eligibility item (“When should someone stop being screened for lung cancer?”). However, more smokers answered correctly (57%) when at least one correct response had to be selected. Greater than 80% of smokers answered two items correctly at baseline, suggesting ceiling effects for these questions: “Can a CT scan find lung disease that is not lung cancer?”, and “Without screening, is lung cancer often found at a later stage when cure is less likely?”
Conclusion: This brief measure of smokers’ knowledge of lung cancer screening with low-dose CT showed good responsiveness with a large improvement in scores after viewing a video-based decision aid. The measure can be used in descriptive studies and serve as an outcome in intervention studies where knowledge improvement is a goal.