Creating case scenarios or vignettes using factorial study design methods.

AIM: This paper is a report of a study conducted to develop clinical case vignettes using an adaptation of an incomplete factorial study design methodology.
BACKGROUND: In health care, vignettes or cases scenarios are core to problem-based learning, common in practice guideline development processes, and increasingly being used in patient or care-giver studies of chronic or life-threatening illnesses. A large number of behavioural, psycho-social and clinical factors can be relevant in such decision problems. Unbiased methods for choosing what factors to include are needed, when it is not possible to include all relevant combinations of factors in the vignettes.
METHOD: The factors to be considered, number of levels or categories for each factor, and desired number of scenarios were decided in advance. An algorithm was used first to create the full factorial data set, and then a random subset of combinations was generated, according to predefined criteria, based on maximizing determinants. The subset of combinations was incorporated into written vignettes. The study was conducted in 2004-2005.
FINDINGS: Application of the method yielded diverse and balanced scenarios that covered the full range of factors to be considered for a project to elicit health providers' processes in diet counselling for dyslipidemia.
CONCLUSION: The approach is flexible, decreases possible researcher bias in the creation of vignettes, and can improve statistical power in survey research. This novel application of study design methodology merits consideration when vignettes are being developed to elicit opinions or decisions in studies of complex health issues.