Cholesterol Risk Calculator Debacle – ctd.

TIE readers are amazing. One writes me, but asks to remain anonymous:

The cholesterol guidelines are part of a move towards risk-based prevention of CVD (as opposed to risk factor based) that’s been going on for about 10 years.

If I understand the Times article correctly (which is difficult because the Lancet paper it’s based on isn’t available yet), it looks like what happened isn’t that the new scores have errors, it’s that they didn’t calibrate in another dataset. Roughly, this means that the average rate of events is different from predicted in one group of people to another. It has been seen in a lot of risk scores before. There are many reasons why this might happen, some that say important things about the score, but just as many that actually relate to sampling biases that are not real threats.

One question is if this makes the transition from LDL to risk in the new guidelines a bad decision. I think it wouldn’t. A man who smokes has 5x the probability of having a heart attack or stroke prevented by a statin as a woman who doesn’t, but the old guidelines treated them identically. A 50% error in calibration does not change that. 

The new guidelines are aggressive. This is a judgment call – what’s an appropriate number needed to treat for preventing a stroke or heart attack vs. the more common side effects of statins. They also could have made a guideline that would have been more amenable to shared decision-making. But this is being read as an attack on using risk instead of LDL, and I don’t think this seriously harms that advance.

I look forward to more debate.


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