Blog | Monday, August 6, 2018

Another guideline problem involves inaccurate CV risk estimation

When the recent lipid primary prevention guideline released in 2013, I was deemed at “high risk” for cardiovascular disease. This article, “Recent Update to the U.S. Cholesterol Treatment Guidelines,” summarizes the guideline. The guideline uses a risk calculator to guide lipid lowering (mostly statin) prescribing.

Many critics (including me) felt that the calculator greatly overestimated CV risk. Since the guideline depends on accurate estimation of that risk, testing and potentially improving the calculator has a high priority.

A recent Annals of Internal Medicine article, “Clinical Implications of Revised Pooled Cohort Equations for Estimating Atherosclerotic Cardiovascular Disease Risk,” tests the original calculator against current cohort data, and then describes 2 new calculators. The article, very statistically technical, shows a marked improvement in these estimates.

Is this a big deal? Let's use my data as an example. I am 69 years old, have a BP of 124/78, total cholesterol 187 and HDL 75. I have never smoked, and do not have diabetes mellitus. Using the guideline endorsed calculator, my 10 year CV risk is 12.9%. The calculator has this suggestion: “On the basis of your age and calculated risk for heart disease or stroke over 7.5%, the ACC/AHA guidelines suggest you should be on a moderate to high intensity statin.”

The newer, better validated and calibrated, calculator estimates my risk at 7.2%. This is a huge difference! With this calculator I do not meet the very aggressive guideline that would suggest that I take a statin.

From the Annals article: ”Approximately 11.8 million U.S. adults previously labeled high-risk (10-year risk ≥7.5%) by the 2013 PCEs [pooled cohort equations] would be relabeled lower-risk by the updated equations.”

This is not a minor issue! How many side effects would we develop in 11.8 million adults? How much money would we spend on medications? We know that labeling patients leads to increased work absenteeism. What other negative outcomes might come or have already come from an inaccurate estimator?

Now a critic might ask why I am so in favor of the newer calculator. Reading the article, and understanding the problems of risk calculators, their data convinces me.

I hope the AHA/ACC read this article and modify their recommendations. I will certainly not start taking a statin given the more accurate estimation.

db is the nickname for Robert M. Centor, MD, MACP. db stands both for Dr. Bob and da boss. He is an academic general internist at the University of Alabama School of Medicine, and the former Regional Dean for the Huntsville Regional Medical Campus of UASOM. He still makes inpatient rounds regularly at the Birmingham VA and Huntsville Hospital. His current titles are Professor-Emeritus and Chair-Emeritus of the ACP Board of Regents. This post originally appeared at his blog, db's Medical Rants.