Tuesday, November 19, 2013

Garbage in Garbage out: problems with guidelines

NYTimes article about the "new" cholesterol guidelines.

This week, cardiologists learned that a new online calculator meant to help them determine a patient’s suitability for cholesterol treatment was flawed, doubling the estimated risk of heart attack or stroke for the average patient. But fixing it would not be easy, because it is based on older data, and heart attack and stroke rates today are much lower than in decades past, meaning that people are at less risk than might be expected from historical extrapolations.

the heart attack and stroke rates have gone down, so the old data is out of date, so they calculate your risk to be too high.
and they don't know the reason behind this change.
and sometimes they calculate it wrong, assuming everything goes on a straight line, when in reality it does not. 

“The model suggests that lowering systolic blood pressure from 130 to 100 is nearly as important as from 180 to 150,” he said. “I doubt there is a cardiologist in the country that believes that.”
not mentioned: if you lower the BP below 130, you end up with fainting patients and broken hips.

actually this is the most disturbing part:
Dr. Blaha and his colleagues discovered the flaws of the calculator based on the Framingham Heart Study a couple of years ago but did not publish their results because they were waiting for the new calculator to appear. They thought any issues with the old calculator would soon be moot. 
uh, fellahs: ever hear of the phrase: "speaking truth to power"?
Scientists are supposed to be dedicated to truth, and not stay quiet because the gov't big shots say something is true.

of course, a lot of us are sceptical and ignored them.
Many doctors never used the Framingham calculator anyway, said Dr. Benjamin Ansell of the University of California, Los Angeles. Instead, they mostly offered statins to people with very high cholesterol levels, ignoring the fact that those who have lower cholesterol levels but other risk factors, like smoking or high blood pressure, often benefited. 
note that last part: it ignores that these lower risk patients might indeed benefit, but that the improved benefit might not be worth the cost and side effects. Which is why I hesitated to give my 80 year old patients treatment for their high cholesterol, and avoided statins in my smoking alcoholics (because it could cause liver disease, not to mention a lot of them didn't take the pills).

and at the very end of the article it notes two things: one, experts don't always get it right, and two, doctors always take these expert's advice with a grain of salt:

Dr. Michael Pignone of the University of North Carolina said it was time to take another look at the new calculator. The guideline committee members are experts, he said, but “getting it right is really hard.”
Dr. Welch went further.
“It should be fixed,” he said. “And before we launch it on the public, we should launch it on the skeptical doctors. This matters to millions of people.”

one of my objections to Obama care is that some gov't bureaucrat will punish docs if they don't obey the guidelines.

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