The evaluation problem in the empirical literature on the impact of pharmaceutical reference pricing

The objective of this paper is to describe empirical studies evaluating the impact of reference pricing interventions in pharmaceutical markets, and to assess the quality of their evaluation method. A total of ten studies were included in the review. The nature of the intervention, the nature of the data available, the nature of the question to be answered, and the requirements of the evaluation method were examined for each study with a questionnaire including 20 questions. The most frequently used evaluation method was the conventional before-after estimator, and only three studies used the difference-indifferences method. Despite the rigorous effort made to evaluate the impact of RP policies in some countries, several limitations may affect both their internal validity (the nature of the data available, statistical problems common to non-experimental data, etc.) and their external validity (heterogeneity in the nature of the intervention).