The opening ceremony of the 2008 Olympic Games in Beijing has yet to take place, but already several athletes face charges of taking substances banned by the International Olympic Committee. These are just the latest in a long line of cases in which competitors have been accused of using performance-enhancing substances. Far from quelling such practices, the advent of drug testing in sport in the late 1960s stimulated an arms race between regulators and the cheats.

Today, some athletes and their coaches continue to risk their reputation, and sometimes the athletes' long-term health, for the chance to dope undetected. In the process, they push the human body to its limits and go beyond what is known about the drugs being taken. The latest drugs are designed with testing in mind, so that they either clear from the body quickly or do not produce the tell-tale metabolite spikes in blood and urine samples. As a result, the testing labs must also push to stay one step ahead of the cheats.

Drug testing should not be exempt from the scientific principles and standards that apply to other biomedical sciences.

On page 692, biostatistician Donald Berry of the University of Texas in Houston outlines what he sees as problems with the way doping tests are conducted. He argues that anti-doping authorities have not adequately defined and publicized how they arrived at the criteria used to determine whether or not a test result is positive. The ability of an anti-doping test to detect a banned substance in an athlete is calibrated in part by testing a small number of volunteers taking the substance in question. But Berry says that individual labs need to verify these detection limits in larger groups that include known dopers and non-dopers under blinded conditions that mimic what happens during competition.

Nature believes that accepting 'legal limits' of specific metabolites without such rigorous verification goes against the foundational standards of modern science, and results in an arbitrary test for which the rate of false positives and false negatives can never be known. By leaving these rates unknown, and by not publishing and opening to broader scientific scrutiny the methods by which testing labs engage in study, it is Nature's view that the anti-doping authorities have fostered a sporting culture of suspicion, secrecy and fear.

Detecting cheats is meant to promote fairness, but drug testing should not be exempt from the scientific principles and standards that apply to other biomedical sciences, such as disease diagnostics. The alternative could see the innocent being punished while the guilty escape on the grounds of reasonable doubt.