Purpose: Existing “gold standard” preference assessment methods may suffer from problems with validity and reliability. Conjoint analysis, a method of consumer preference measurement, may have superior comparative performance characteristics. We aimed to conduct a randomized comparison of methods in men at risk for prostate cancer.
Method: Men who had undergone treatment for localized prostate cancer were interviewed individually to identify attributes of prostate cancer treatment that were critical to patients. Using these attributes, we developed 3 preference assessment applications: rating scale (RS), time trade-off, (TTO) or conjoint analysis-based (CA). These applications were first piloted in men who had been treated for prostate cancer. We then randomized men who had undergone prostate biopsy with negative results to preference assessment with the CA and either TTO or RS applications. Validity of preference measurement was compared by assessing the ability of the utility functions derived from each application to successfully predict the patient’s preference for novel multi-attribute health states that he had not yet seen or rated. We compared the internal consistency and predictive validity of each method at the individual level as well as the perceived difficulty and effectiveness of each task. We compared the most important treatment attributes identified by each method.
Result: 17 subjects have been randomized to date. Average age was 64 years, range 55 – 71, 29% were Caucasian, 47% were African-American, 25% other. Educational attainment was 12% High School, 53% some college, 35% college graduate. The CA and RS methods had high internal consistency compared with TTO (average r2 of 85% (CA), 86% (RS) and 44% (TTO). Utility functions derived from CA and RS were superior at prediction of preference for novel multi-attribute health states compared with that of TTO. The most important three attributes to patients as determined using CA were effect on urinary function, sexual function and surgery avoidance. These differed from those identified using RS and TTO in the inclusion of surgery avoidance instead of bowel function. Patients felt CA was the most difficult method, but also the most effective at expressing their values.
Conclusion: Conjoint analysis is a feasible method of preference assessment in men at risk for prostate cancer, and is viewed as effective by such patients. Both RS and CA outperform TTO based on preliminary results.