Purpose: We sought to compare, in a randomized trial, two techniques for eliciting and clarifying patient values for decision making about colorectal cancer (CRC) screening: conjoint analysis and a rating and ranking exercise.
Method: Based on our past research and a review of the literature, we identified 6 key attributes of CRC screening tests: 1) ability to reduce CRC incidence and mortality; 2) test-related discomfort; 3) nature of the test (where performed, time required); 4) test frequency; 5) major complications; and 6) out of pocket costs. Using our decision lab registry and university email lists, we recruited adults ages 48-75 who were at average risk for colorectal cancer for a written, mailed survey. Eligible participants were given basic information about CRC screening and then randomized to complete either a choice-based conjoint analysis with 16 discrete choice tasks or a rating and ranking exercise. Outcomes included most important attribute, as determined from conjoint analysis or participant ranking; values clarity (sub-scale of the decision conflict scale), intent to be screened, and unlabelled test preference, as assessed on a post-task questionnaire. Conjoint analysis most important attribute was based on individual patient-level utilities generated using multinomial logistic regression and a hierarchical Bayesian modeling approach implemented in Sawtooth software.
Result: 114 respondents were eligible and randomized (54 to conjoint analysis and 60 to rating and ranking) and 104 (50 conjoint analysis, 54 rating/ranking) completed and returned questionnaires. Mean age was 57 (range 48-73), 70% were female, 88% were White, and 71% were college graduates. 62% were up to date with CRC screening, with most having had colonoscopy. Ability to reduce CRC incidence and mortality was the most frequent most important attribute for both the conjoint analysis (56% of respondents) and rating/ranking (76% of respondents) groups, but this proportion differed significantly between groups (absolute difference 20%, 95% CI 3%, 37%, p =0.03). There were no significant differences between groups in proportion with clear values (p=0.352), intent to be screened (p=0.226) or unlabelled test preference (p=0.521)
Conclusion: A choice-based conjoint analysis task produced somewhat different patterns of attribute importance than rating and ranking exercises, but had little effect on other outcomes in this small trial. Larger trials comparing these values clarification techniques and measuring their effect on screening behavior are warranted.