Stroke-preventing devices are not being tested in people who resemble the patients most likely to receive them, a new study shows. The researchers looked at tests being done as part of "post-market surveillance studies," which test products that are already approved and in general use by the public. They found that patients who had stents placed into their neck in these studies were healthier than other patients in a broader nationwide registry of people who received stents. Yet the patients in the larger registry database who weren't in the post-marketing studies were 50% more likely to have had a stroke in the past, and were four times as likely to die in the hospital.