28 August 2010

Surrogate markers, in medicine and policy

A surrogate marker is an event or a laboratory value that researchers hope can serve as a reliable substitute for an actual disease. A common example of this is blood cholesterol levels. These levels are surrogates, or substitutes, for heart disease. If a medical study demonstrates that a medication can lower cholesterol level 10%, then we assume that this will also lower the risk of cardiovascular disease. Why doesn’t this same study determine if an anti-cholesterol drug decreases heart attack rates directly? After all, most folks would rather be spared a heart attack than have a silent decrease in their blood cholesterol levels. ...Surrogates often take on a life of their own, far removed from the actual disease they represent. Patients shouldn’t care if their ‘surrogates’ are improving; their objective should be to prevent disease, feel better and live longer. Evidence-based medicine in disguise: beware the surrogate, 'MD Whistleblower' (blog by Michael Kirsch), 1 August
Quite so. And as in medicine, so it is in policymaking, and for much the same reasons: 'It's much easier and cheaper ...to measure surrogates than actual disease events.' It's much, much easier to measure a government agency's spending than it is to measure its success or otherwise in delivering meaningful outcomes.

The problem isn't always that of measurement, or of short-term interests trumping long-term benefits. There is also the inescapable subjectivity of an important components of welfare: psychological wellbeing. To take one example that has obvious policymaking implications: in the UK for several years crime appears to have fallen, while fear of crime has risen (see here). The answer, if there is one, might be to re-localise some policymaking. Some of the most important components of wellbeing simply cannot be quantified and aggregated for efficient use by our highly centralised bureaucracies. Withdrawing unemployment benefit, for instance, could actually help someone who's lacking in motivation and would gain by being made to find a job. To another person, though, the loss of a welfare payment could mean calamity. No bureaucracy can make such a distinction, and we might not want one with the intrusive powers that could.

Social Policy Bonds are no different from conventional policy in that respect, except that they have to answer, upfront, the difficult question of whether a specified goal is a surrogate (a supposed means to an end) or an end in itself. Having to do that at the outset of making policy, is probably an advantage over the current system in which, too often, objectives are vague, conflicting, and only tenuously related to policy instruments allegedly supposed to bring them about.

No comments: