Most people don’t know it, but hard evidence as to which medical treatments actually work best is in awfully short supply here in the U.S. The growing scandal over the expensive cholesterol drug Vytorin, which appears to be no more effective than older, cheaper statin drugs, is just the latest example, since data on the drug’s usefulness didn’t emerge until four years after Vytorin was approved — and almost not even then.

It’s hard to overstate the seriousness of the problem. As Shannon Brownlee documents in her new book “Overtreated,” between a fifth and one-third of total U.S. healthcare spending covers treatments that do nothing to improve health, and which in fact often harm patients by exposing them to the risks of avoidable surgeries, hospital-acquired infections and a variety of medical errors. Brownlee cites one estimate that unnecessary care may kill as many as 30,000 Americans a year. (I’ll have more on “Overtreated” in future posts.)

So the news from Reuters (via Pharmalot) that Senators Max Baucus and Kent Conrad (both Democrats) will push to create an independent institute that will study how well new medical devices and drugs stack up against existing treatments — one funded at $200 million a year — comes none too soon. While that bill probably won’t make it into law any time soon, it at least puts down an important marker in advance of the broader debate over healthcare reform that’s likely next year. Both the Clinton and Obama health plans also advocate establishing similar institutes.

(My only quibble, actually, is that comparative effectivness shouldn’t be restricted to drugs and devices. Surgical procedures and medical imaging such as CT scans and MRIs also contribute mightily to unnecessary medical treatment.)

Comparative-effectiveness research isn’t perfect, of course, as the often controversial history of Britain’s decade-old National Institute of Clinical Evidence suggests. It’s also clear that the drug and device industries — quite likely joined by doctors who have profited handsomely under current arrangements — will pull out the stops in opposition. (These groups share a not-entirely-unjustified fear that comparative-effectiveness findings could be used to cut payments for newer, lucrative technology and procedures.) What’s more, even solid research results don’t always change the established behavior of doctors and hospitals, at least not in the short run.

But given the increasingly obvious shortcomings of industry-funded research — including the studies used to justify regulatory approval by the FDA — any move toward closing medicine’s little-understood “evidence gap” has to count as a step in the right direction.

(Image courtesy of Flickr user xmatt under Creative Commons.)