A brief measure of Smokers' knowledge of lung cancer screening with low-dose computed tomography

• Lung cancer screening with low-dose CT is recommended for high risk smokers.
• Smokers must understand harms and benefits in making informed screening decisions.
• A brief measure of lung cancer screening knowledge is offered.
• The measure assesses key concepts in making informed screening decisions.
• It can be part of a broader assessment of the quality of screening decisions.

We describe the development and psychometric properties of a new, brief measure of smokers' knowledge of lung cancer screening with low-dose computed tomography (LDCT). Content experts identified key facts smokers should know in making an informed decision about lung cancer screening. Sample questions were drafted and iteratively refined based on feedback from content experts and cognitive testing with ten smokers. The resulting 16-item knowledge measure was completed by 108 heavy smokers in Houston, Texas, recruited from 12/2014 to 09/2015. Item difficulty, item discrimination, internal consistency and test-retest reliability were assessed. Group differences based upon education levels and smoking history were explored. Several items were dropped due to ceiling effects or overlapping constructs, resulting in a 12-item knowledge measure. Additional items with high item uncertainty were retained because of their importance in informed decision making about lung cancer screening. Internal consistency reliability of the final scale was acceptable (KR-20 = 0.66) and test-retest reliability of the overall scale was 0.84 (intraclass correlation). Knowledge scores differed across education levels (F = 3.36, p = 0.04), while no differences were observed between current and former smokers (F = 1.43, p = 0.24) or among participants who met or did not meet the 30-pack-year screening eligibility criterion (F = 0.57, p = 0.45). The new measure provides a brief, valid and reliable indicator of smokers' knowledge of key concepts central to making an informed decision about lung cancer screening with LDCT, and can be part of a broader assessment of the quality of smokers' decision making about lung cancer screening.