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 drug treatments and other resources tend to vary dramatically between institutions. Drugs that were prohibitively expensive in one analysis can be most dominant (both more effective and less expensive) from another institution's perspective.

In the United States some authors try to get around this problem by using published average wholesale prices supplied by the manufacturer. These are, however, usually a dramatic overstatement of the amounts paid by any real purchaser (including the perspective of retailer or consumer).

The remedy to this problem probably lies in authors publishing (or making available on software) both the description and number of each type of healthcare resource used with the price or cost assigned to it. In that way, someone in the United Kingdom or Poland, or even another state in the United States, could substitute either their own unit price or number of resources they consumed. Rather than saying that an operation costs $10 000, if I knew it comprised four days in hospital at a cost of $2500 a day, I could open up a computer spreadsheet and rerun the analysis using my own assumptions on the basis of the standard of care in my institution or setting and my cost per unit consumed in that setting.

Unfortunately, such information is often lacking. In my unpublished research on 125 studies (1996-2001) of cost effective devices in surgery, only five articles listed the unit costs, two listed the number of units consumed, and none listed both. The best information that can typically be found in even a great analysis is the cost per unit consumed (even that is often concealed for the sake of preserving proprietary information).

Authors and sponsors of pharmacoeconomic research need to realise that decision makers require an analysis that is sufficiently transparent; it can be customised for their own setting and include access to the underlying costs and resource consumption. Until then, I will continue to have doubts as to the extent to which such published material is being used by decision makers in any country.