Although most variations in results among countries are probably due to
chance, variations can occasionally reflect important differences among
countries in either the true benefits of an intervention or its true
harms. When a randomized, clinical trial shows marked variations in
results among countries, one should seek supporting evidence to
understand whether the observed results are likely to be real, an
artifact of the design analysis or implementation of the trial, or
simply due to chance.
http://www.nejm.org/doi/full/10.1056/NEJMra1510065?query=TOC-the question is critical as for example the RCT that support the use of sacubitril in heart failure has no significant effect in Europe