Validating the analytic hierarchy process for eliciting colorectal cancer screening preferences in an online questionnaire

Background The expected impact of screening on health-related quality of life influences peoples’ decision to participate in screening programs. In addition, factors like risks and discomfort associated with the screening determine individuals’ attendance of the test. To maximise the participation and hence the net benefit of a screening program for colorectal cancer, it is important to know the preferences of the screening population on different screening methods. Objective The objective of this study was to validate the Analytic Hierarchy Process (AHP) in measuring patient preferences for colorectal cancer screening in an online survey and to explore to what extent AHP can be used to predict the impact of offering different screening technologies on screening attendance. Study population Dutch men and women aged 55 to 75 years. Excluded are people who already have or had colorectal cancer or a colon infection and people who are already in a colorectal cancer check-up program or people have been advised to do so. Methods Respondents were asked to fill in a web-based questionnaire consisting of four different scales to measure their colorectal cancer screening preferences: (1) the AHP questions, (2) questions about the intention to attend the screening, (3) a question about the direct ranking of the screening methods and (4) a quality of life rating scale. The AHP model consists of four main criteria: sensitivity, specificity, safety and burden (which consists of the two sub criteria inconvenience and frequency). Four alternatives are included: iFOBT, Colonoscopy, Sigmoidoscopy and Virtual Colonoscopy. Results 650 of the 1542 respondents filled in the questionnaire, of which 167 were consistent in their answers on the AHP questions. The most preferred screening methods were iFOBT and Virtual Colonoscopy which is measured with all four scales. From the data, however, it seemed that the respondents to the online AHP survey were not able to judge clinical traits as sensitivity, specificity and safety (i.e. risks) in accordance with the risk information provided. When comparing the AHP scale with the other scales, it correlates best with direct ranking scale. When comparing the intention to attend scale with the other scales, it correlates the worst with AHP. Conclusion The Analytic Hierarchy Process can be used in an online questionnaire to measure patient preferences for colorectal cancer but it seems only partially valid, depending on which criteria are used in the AHP model. That is, it appears not valid for measuring clinical traits like sensitivity, specificity and safety or risks. On the other hand the correlations show us that when comparing the intention to attend scale with the other scales, it correlates the worst with AHP. Therefore it is questionable if AHP is the best way to predict impact of offering different screening technologies on screening attendance. However, predicting the intention to attend (or the actual attendance) and eliciting preferences is not the same thing. Hence the AHP model should be adjusted for this by selecting different criteria. When this is done, AHP has potential to be a good predictor for the intention to attend or the actual attendance.