Currency conversion is not only issue in effectiveness studies

EDITOR—Gosden and Torgerson mention that currency conversions make the use of foreign pharmacoeconomic analyses of questionable value.1 I agree that currency conversion is a difficult task, particularly when the euro to dollar exchange rate has gone from 1:0.80 to 1:1.08 in less than two years. But the problem of external validity or usefulness in other settings goes far beyond currency conversion issues.

Even in the same country, published analyses tend to be of little value because the underlying prices or costs of the …