A report released today in the British Medical Journal (BMJ) reveals how most drug trials assume that patients respond consistently to treatment, but the assumption is rarely tested.

The research carried out by Professor Stephen Senn, Department of Statistics University of Glasgow, explains how if patients vary randomly in their response to a drug rather than some patients never responding, searches for a genetic basis for non-response are futile.

Imagine a trial with 1000 representative patients, each given the chance to try a new treatment once. Seven hundred succeed in the treatment and the other three hundred fail. How should we interpret these results?

The common assumption is that the treatment works for 70% of patients 100% of the time and for 30% of the patients 0% of the time. However, nothing in the data forbids a radically different interpretationﾗnamely, that the treatment works in 100% of the patients 70% of the time. In the first case, ability to succeed on treatment is a permanent feature of the patient. In the second case, individual response cannot be predicted: the patients are indistinguishable from each other regarding response to treatment. They sometimes respond and they sometimes do not. Intermediate cases between these two extremes are, of course, also possible.

For more details of this case study, and other cases, see: BMJ Website.

The pharmaceutical industry has rarely, if ever, carried out the sort of trial that would permit identification of patient treatment by interaction. Thus statements that the drugs don't work on most people are based on mere supposition; the drugs may work moderately well for all people. To identify those drugs and disease combinations for which individual response is important and hence for which genetic factors may be, it will be important to plan and analyse carefully.

Media Relations Office (media@gla.ac.uk)

Full details of the report entitled ?Individual response to treatment: is it a valid assumption?? can be found at the: BMJ Website.

For more details please contact Professor Stephen Senn on 0141 330-5141. Alternatively contact Mike Findlay at the University Press Officer on 0141 330-3535.

First published: 22 October 2004