What is required to evaluate the impact of pharmaceutical reference pricing?

Objective: To describe empirical studies evaluating the impact of reference pricing (RP) interventions in pharmaceutical markets in order to discuss the requirements for these evaluations. Methods: Ten studies were included in this review. For each study, 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 through a questionnaire. The most frequently used evaluation method was the conventional before-after estimator, and only three studies used the difference-in-differences method. Results: Nine studies evaluated a therapeutic RP system and one evaluated a generic RP system. All of the papers reported how the reference price level was established, but only one study directly reported the updating frequency and criteria of the RP system. In four studies, details of simultaneous interventions were not reported. There is no paper providing evidence on overall social welfare impact. Four papers estimated the impact of intervention on the consumer price of drugs covered by the RP system. Only one provided information about the impact on the price of related drugs not covered by the system. Three studies included an outcome variable for the use of health services. The impact of RP intervention on the level of competition in the market for those medicines covered by the system was reported in only three of ten papers. Discussion/conclusion: 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). © 2005 Adis Data Information BV. All rights reserved.