COMMENTARY

New Lipid Guidelines: A Primary Care Perspective

Kenneth W. Lin, MD, MPH

Disclosures

November 30, 2018

Editorial Collaboration

Medscape &

Hello, everyone. I'm Dr Kenny Lin, a family physician at Georgetown University Medical Center in Washington, DC, and I blog at Common Sense Family Doctor.

The American College of Cardiology/American Heart Association (ACC/AHA) recently updated their 2013 cholesterol management guideline,[1] and though there has been plenty of news and commentary on the similarities and differences between the new guideline and the old, I would like to provide a primary care perspective on a few key points.

First, how trustworthy is this guideline? The American Academy of Family Physicians gave the 2013 version a qualified endorsement due to concerns about its reliance on a new risk assessment tool, financial conflicts of interest in nearly half of the panel members, and the many recommendations that were based on expert opinion rather than on patient-oriented evidence. I will get to the risk assessment tool in a moment, but a major improvement in the new guideline is that none of the panel members had conflicts of interest.

The panel carefully evaluated the frequency and severity of statin-associated side effects such as myalgias and diabetes, and their implications for shared decision-making discussions with patients about potential benefits and harms of therapy. On the other hand, an independent systematic review[2] was performed for only one of the major recommendations. This review found that in very high-risk persons with known cardiovascular disease who are already taking statins, adding ezetimibe or PSCK9-inhibitors provided additional risk-reducing benefits over statin therapy alone.

The new guideline uses the same Pooled Cohort Equations calculator to estimate 10-year cardiovascular disease (CVD) risk as the previous guideline. Several population-based studies[3] that evaluated the Pooled Cohort Equations found that they overestimate CVD events by 20% overall and are less accurate when applied to individuals. Recently, a group of outside researchers proposed revising the Pooled Cohort Equations by using more recent data and statistical methods[4] to improve accuracy of risk prediction in black adults, for whom the calculator sometimes performs poorly in comparison to whites with similar risk factors. Rather than adopting the revised calculator, the guideline suggests considering an individual's calculated risk as a starting point for discussion rather than a precise estimate, especially in the "intermediate risk" zone of 7.5% to 20%. The guideline also provides a list of "risk enhancers" that may favor statin use, including a family history of premature CVD, metabolic syndrome, premature menopause, and South Asian ancestry.

If the clinician and patient are still uncertain about starting a statin, the guideline advises measuring coronary artery calcium (CAC) in selected adults and not prescribing a statin if the CAC score is 0. CAC scans cost around $200 and are associated with radiation exposure. The incremental value of adding CAC to traditional risk assessment has been debated for some time.[5] Studies have found that measuring CAC score modestly improves risk classification beyond the Pooled Cohort Equations[6] and may be associated with improvements in CVD risk factors.[7] However, the US Preventive Services Task Force found insufficient evidence that performing CAC scans in intermediate-risk persons improves CVD outcomes.[8]

A large, ongoing randomized trial in Europe is comparing the outcomes of therapy based on CAC screening with therapy based on traditional risk factor assessment, but results are not expected for at least 5 years.

In summary, I commend the ACC/AHA for eliminating conflicts of interest from the panel that developed its new cholesterol guideline, and for providing primary care physicians with more flexible guidance on statin prescribing decisions, given the limitations of estimating risk with the Pooled Cohort Equations. Given the additional cost and potential harm of a CAC scan and the lack of evidence that it improves outcomes, clinicians should order these scans rarely, and only if there is a strong likelihood that the results would change therapy.

This has been Dr Kenny Lin for Medscape Family Medicine. Thank you for listening.

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