International differences in trial results

Many researchers accept that the efficacy of treatments may differ between countries, and that differences need to be considered when assessing the potential benefits of treatments whose trials were conducted in a different country. The CLAHRC WM Director has recently had a paper published on international differences in the results of cardiovascular trials, looking at 59 meta-analyses of RCTs.[1] In most meta-analyses, relative to the control, the intervention was more favoured in trials conducted in Europe than those in North America for non-fatal endpoints (70% of meta-analyses, P=0.017), while there were non-statistically significant differences for fatal endpoints (65% of meta-analyses, P=0.066). It was not possible to determine which types of interventions were more likely to show international differences. The size of the effect, though significant for non-fatal outcomes, was small and the results of trials travel reasonably well across the North Atlantic.

— Richard Lilford, Director CLAHRC WM


  1. Bowater RJ, Hartley LC, Lilford RJ. Are cardiovascular trial results systematically different between North America and Europe? A study based on intra-meta-analysis comparisons. Arch Cardiovasc Dis. 2014. [ePub].

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