A running joke about revalidation is that its roll out is and always will be 12 to 18 months away. What will mandarins in Whitehall and the colleges chuckle about now that revalidation has finally started? Almost as important, will revalidation work and what impact will it have on the working lives of doctors, standards of medical care, and the safety of patients? Will it be worth the cost?

The answer is not completely clear. Revalidation is a form of assessment and so it should have high validity and reliability, it should be acceptable to stakeholders, and it should have a positive impact on the behaviour of those undergoing the assessment. It should also be low cost. How revalidation scores on all these criteria isn’t clear at present because it hasn’t started. However working from first principles there are some things that we can say about the utility of revalidation.

First of all, costs. To make revalidation work the following main costs will need to be accounted for—the costs of the time of appraisees, appraisers, responsible officers, managers, and administration staff, and the costs of facilities and information technology. For over 100 000 doctors, these costs will add up. Secondly, validity. Revalidation seems to have good face validity—it seems like it will do what it says on the tin—the only problem with this is that face validity is a vague, meaningless, and discredited concept. Construct validity and criterion validity are better—but will require proving. Thirdly, there is reliability, and here only time (and properly conducted studies) will give us pointers as to the reliability of revalidation. Fourthly, acceptability. Most doctors have accepted that revalidation is inevitable and that it is not an insurmountable obstacle in its current format. The regulator (the GMC) obviously feels that it is acceptable. The only question that remains is whether revalidation is and will be acceptable to patients and the public. Will public confidence in the scheme remain if doctors who have passed revalidation are subsequently found to be incompetent? And fifthly, impact, and here there are grounds for optimism. Preparing for revalidation should at the least involve doctors in doing lots of education, in taking part in quality improvement projects, and in doing 360 degree appraisals—all of which should encourage them to be the up-to-date medical professionals that we want. Useful feedback following appraisals should further drive behaviours in the right direction.

And the final question—will it be worth the cost? Only cost benefit studies will give us the answer. Even though there has been rhetoric about cost effective approaches, in the case of revalidation, cost effectiveness studies are not appropriate. This is because no intervention is cost effective in and of itself—it must be cost effective compared to an alternative. Currently there are no plans for other means of keeping doctors on the register other than those outlined in revalidation. Cost benefit studies are needed but they will require careful planning, time, and funding.

Kieran Walsh is clinical director of BMJ Learning—the education service of the BMJ Group. He is responsible for the editorial direction of BMJ Online Learning, BMJ Masterclasses, and BMJ onExamination. He has written two books—the first on cost and value in medical education and the second a dictionary of medical education quotations. He has worked in the past as a hospital doctor – specialising in care of the elderly medicine and neurology.