OBJECTIVES:

International drug price comparisons are increasingly used to rank countries according to the drug price level, and to evaluate their pricing and policy systems. However, they often present multiple methodological biases which involve numerous uncertainties on the results. The objective of this work is to make an inventory of the latest studies that compared drug prices in OECD countries and to assess their methodological quality using a reading grid developed for this purpose.

METHODS:

The literature research focused on drug price comparisons studies performed in OECD countries, using notably the terms “international”, "drug prices," and "comparative study", whose were referenced in Pubmed and published between 2008 and 2017. Literature recommendations on price comparison studies’ design were updated using a grid composed by 22 criteria in 7 seven categories (including drug inclusion scope, data sources, price compared, or currency conversion). For each criterion, depending on its presence (Yes, No, No but discussed), and its level of recommendation (9 recommended items, 13 mandatory items), a methodological reserve could be rated as minor or moderate, major, or as none.

RESULTS:

Twenty-seven studies were retrieved. Eight were published in 2017. Those studies compared on average 9.7 countries, on various therapeutic areas, often on the top selling drugs. We estimated an average of 5.35 major (minimum: 2; maximum: 8) and 5.00 moderate methodological reserves by study. For instance, on the mandatory criterion: “If the results are presented globally the study uses price indexes (Laspeyres index is preferred) to weight the prices” only six studies met this requirement.

CONCLUSIONS:

Even though the ideal method to overcome biases in drug price comparisons studies does not exist because of lack of data, major methodological biases could be avoided. A standardized methodology should be used to obtain transparent drug price comparisons, therefore a better political relevance.