Run-ins over consent

One of the lessons from Susan Reverby's discussion of the Tuskegee experiment ("We're sorry we lied and let you die", THES, August 4) is the importance of informed consent. She is surely right in arguing for continued vigilance.

One way informed consent is regularly flouted is in the use of so-called "placebo run-ins". These are periods at the start of a clinical trial in which all patients are given a placebo. The fact that this is being done is not explained to patients, since this would render this stratagem useless.

I am not suggesting placebo run-ins are a modern Tuskegee. Nevertheless, this feature of many trials, which is in any case of little scientific value, is to be regretted, not least because in the long run it will contribute to further erosion of patient's trust in physicians and may jeopardise the use of placebos as controls in clinical trials, for which purpose they can be both ethical, given consent, and scientifically valuable.

Stephen Senn Professor of pharmaceutical and health statistics University College London