Of course, the situation is not quite as simple as this. Selling insurance, one could argue, is not the same as inviting a patient to take part in a clinical trial. If the doctor was not reimbursed generously for his time then important clinical research would just not get done.¹ The doctor can be trusted to put the best interests of the patient above personal gain, and therefore telling potential trial subjects how much the doctor will be paid is unnecessary. Do these arguments stand up to closer scrutiny? Or has the practice and scale of payments reached a point where it has become harmful to the conduct of good research?

Randomised clinical trials, often sponsored by pharmaceutical companies with a valid commercial as much as a genuinely scientific interest, are the only reliable way to generate good quality evidence of efficacy.² Clinicians ideally should be in equipoise about the treatments being tested,³ and patients should give voluntary consent based on full disclosure of relevant information.⁴ The practice of paying doctors to recruit patients under their care, and not disclosing this pecuniary interest, corrupts both these ideals.

Over the years we have seen the payments on offer soar to thousands of pounds per completed patient. Well organised British general practices can earn an extra £15000 annually for three hours' work a week.⁷ As a result, trials designed by non-commercial sponsors aiming to answer clinically important questions but without the funding available to pay recruiters fail to attract doctors.⁸ So called postmarketing research (phase IV studies) is the biggest culprit. As uncontrolled observational cohort studies, these studies make no attempt to address important areas of clinical uncertainty. Their stated purpose is to familiarise doctors with new and recently licensed drugs.⁹ This is marketing thinly disguised as research and is greatly helped by—and probably not possible without—a system of undisclosed payments.

Payments, often overtly on a per capita basis, have reached levels that are of serious concern to research ethics committees. Commercial sponsors regularly flout the implicit ban on per capita payments by claiming to pay for the work involved in conducting the trial (rather than for recruiting patients), and then overestimating the amount of time required for each patient. Such payments are in addition to the doctor's regular income and can result either in overwork or in displacing other more pressing clinical activity. Anecdotally we have heard that some hospital departments depend on regular income from patient recruitment and that some general practitioners have set up systems to trawl their databases to find patients who fit the requirements for a particular sponsor's study to improve their recruitment rates.

The lack of disclosure to patients can potentially be damaging. We acknowledge the potential for unethical practice by requiring that the amount and basis of payments are disclosed to a research ethics committee. However, this does not go far enough. Not to require a similar disclosure to patients is as cynical as it is demanding of blind and unquestioning trust. Patients who take part in trials do so at least partly from altruism.¹¹ Failure to reveal the conflict of interest that is inherent in payments that doctors receive from the trial sponsors is not a good basis for involving patients in the research endeavour. One American study found that just over half of patients questioned found payments to clinicians unacceptable. An even greater proportion (80%) believed that the patient had a right to know that their doctor would be paid for enrolling them (see figure).⁹