BACKGROUND: Concerns that there are international differences in treatment effectiveness have led many countries to be reluctant to extrapolate foreign clinical data to use as the basis of their guideline recommendations and in the approval of new interventions. Much of the evidence on which these concerns are based, however, comes from a limited data set, with few studies directly assessing international differences in treatment effectiveness. The aim of this study was to assess differences in the results of cardiovascular trials between Europe and North America and further, investigate if certain intervention types were more prone to such differences. This was done using the panoramic meta-analytic approach.
METHODS: A literature search was conducted over the Cochrane Library (2000 to 2008) and Medline (2005-2008) for all meta-analyses which contained randomised control trials for the treatment or prevention of cardiovascular diseases. The analysis was then conducted both within and over the included meta-analyses by comparing the trial results between Europe and North America for both fatal and non-fatal endpoints.
RESULTS: Over all meta-analyses, for fatal endpoints, interventions conducted in Europe showed more beneficial effects over controls compared to North America but this was not statistically significant. A similar pattern was seen for non-fatal endpoints with this reaching statistical significance (p = 0.017). The types of intervention prone to inter-continental differences could not be identified for fatal or non-fatal endpoints. Methodological quality of individual trials between continents was assessed with the Jadad scale and no statistically significant differences were seen between Europe and North America (p = 0.274).
CONCLUSIONS: Some evidence, although not strong, is provided that international differences in treatment effectiveness exist between Europe and North America. This suggests that those developing guidelines and approving new interventions should be cautious about the extrapolation of trial data between continents.
