Clinical Context

Lp(a) is an established independent risk factor for cardiovascular disease, and current guidelines from Europe, China, and Canada recommend a screening test for Lp(a) at least once in a person’s lifetime. Nonetheless, multiple factors have slowed its use in clinical practice. An editorial by Morris and colleagues, which accompanies the current study, enumerates some of these issues. First, the particle itself is heterogenous, making accurate and reproducible assays for Lp(a) a challenge. Perhaps more important, there are no treatments that substantially reduce Lp(a).

Another barrier to the routine use of Lp(a) is confusion regarding cutoff levels associated with higher risks for atherosclerotic cardiovascular disease (ASCVD) and familial hypercholesterolemia (FH). The current study addresses this issue.

Study Synopsis and Perspective

Many more people are at risk for early cardiovascular events because of raised Lp(a) levels than from having familial hypercholesterolemia (FH), a new study suggests.

The Danish study set out to try and establish a level of Lp(a) that would be associated with a cardiovascular risk similar to that seen with FH. As there are many different definitions of FH, results showed a large range of Lp(a) values that corresponded to risk levels of the different FH definitions.

However, if considering one of the broadest FH definitions (the one from MEDPED [Make Early Diagnoses, Prevent Early Deaths]), which is the one most commonly used in the United States, results showed that the level of cardiovascular risk in patients with this definition of FH is similar to that associated with Lp(a) levels of around 70 mg/dL (0.7 g/L).

“While FH is fairly unusual, occurring in less than 1% of the population, levels of Lp(a) of 70 mg/dL or above are much more common, occurring in around 10% of the White population,” Børge Nordestgaard, MD, Copenhagen University Hospital, Copenhagen, Denmark, told theheart.org | Medscape Cardiology. Around 20% of the Black population have such high levels, whereas levels in Hispanics are in between.

“Our results suggest that there will be many more individuals at risk of premature [myocardial infarction] or cardiovascular death because of raised Lp(a) levels than because of FH,” added Dr Nordestgaard, the senior author of the current study.

Dr Nordestgaard explained that FH is well established to be a serious condition. “We consider FH to be the genetic disease that causes the most cases of early heart disease and early death worldwide.”

“But we know now that raised levels of Lp(a), which is also genetically determined, can also lead to an increased risk of cardiovascular events relatively early in life, and when you look into the numbers, it seems like high levels of Lp(a) could be more common than FH. We wanted to try and find the levels of Lp(a) that corresponded to similar cardiovascular risk as FH.”

The Danish study was published in the November 22 issue of the Journal of the American College of Cardiology.^[1]

The authors note that the 2019 joint European Society of Cardiology and European Atherosclerosis Society guidelines suggested that an Lp(a) level higher than 180 mg/dL (0.8 g/L) may confer a lifetime risk for heart disease equivalent to the risk associated with heterozygous FH, but they point out that this value was speculative and not based on a direct comparison of risk associated with the 2 conditions in the same population.

For their study, Dr Nordestgaard and colleagues analyzed information from a large database of the Danish population including 69,644 individuals for whom data on FH and Lp(a) levels were available. As these conditions are genetically determined and the study held records on individuals going back several decades, the researchers were able to analyze event rates during a median follow-up time of 42 years.

Results showed that Lp(a) levels associated with MI risk equivalent to that of clinical FH ranged from 67 to 402 mg/dL, depending on the definition used for FH. The Lp(a) level corresponding to the MI risk for genetically determined FH was 180 mg/dL.

In terms of risk for ASCVD events, the levels of Lp(a) corresponding to the risk associated with clinical FH ranged from 130 to 391 mg/dL, and the Lp(a) level corresponding to the ASCVD risk for genetically determined FH was 175 mg/dL.

He estimated these individuals have approximately a doubling of cardiovascular risk compared with the general population, and that risk increases further with rising Lp(a) levels.

Although a specific treatment for lowering Lp(a) levels is not yet available, Dr Nordestgaard stresses that it is still worth identifying individuals with raised Lp(a), as efforts can be made to address other cardiovascular risk factors.

Although a level of Lp(a) of around 70 mg/dL confers similar cardiovascular risk than some definitions of FH, Dr Nordestgaard says that lower levels than this should also be a signal for concern. 

“We usually say Lp(a) levels of 50 mg/dL are when we need to start to take this seriously. And it’s estimated that about 20% of the White population will have levels of 50 mg/dL or over, and even more in the Black population,” he added. 

In an accompanying editorial, Pamela Morris, MD, from the Medical University of South Carolina, Charleston; Jagat Narula, MD, from the Icahn School of Medicine, New York City; and Sotirios Tsimikas, MD, from the University of California San Diego, say, “The weight of evidence strongly supports that both genetic lipid disorders, elevated Lp(a) levels and FH, are causally associated with an increased risk of premature ASCVD and should be carefully considered in risk assessment and management for ASCVD risk reduction.”

“But this should not take away the importance of screening for raised Lp(a) levels,” she stressed.

Dr Morris agrees with Dr Nordestgaard that raised levels of Lp(a) may actually be more important for the population risk for cardiovascular disease than FH, as the prevalence of increased Lp(a) levels is higher.

Dr Morris points out that cardiovascular risk starts to increase at Lp(a) levels of 30 mg/dL (75 nmol/L).

The editorialists recommend that, “In addition to performing a lipid panel periodically according to evidence-based guidelines, measurement of Lp(a) levels should also be performed at least once in an individual’s lifetime for ASCVD risk assessment.”

They conclude that, “It is vital to continue to raise awareness among clinicians and patients of these high-risk genetic lipid disorders. Our understanding of both disorders is rapidly expanding, and promising novel therapeutics may offer hope for prevention of [cardiovascular disease] in patients with elevated Lp(a) levels in the future.”

This work was supported by Copenhagen University Hospital-Herlev Gentofte, Denmark, and the Danish Beckett-Foundation. The Copenhagen General Population Study is supported by the Copenhagen County Foundation and Copenhagen University Hospital-Herlev Gentofte. Dr Nordestgaard has been a consultant and a speaker for AstraZeneca, Sanofi, Regeneron, Akcea, Amgen, Kowa, Denka, Amarin, Novartis, Novo Nordisk, Silence Therapeutics, Abbott, and Esperion.

J Am Coll Cardiol. Published online November 14, 2022.

Clinical Implications

• Current guidelines from Europe, China, and Canada recommend a screening test for Lp(a) at least once in a person’s lifetime. Nonetheless, multiple factors have slowed its use in clinical practice. Lp(a) itself is heterogenous, making accurate and reproducible assays for Lp(a) a challenge. Also, there are no treatments that substantially reduce Lp(a).
• The current study finds that Lp(a) values of 70 mg/dL or more are roughly equivalent to a diagnosis of FH using clinical criteria.
• Implications for the healthcare team: The healthcare team should be aware of the risk for ASCVD associated with Lp(a) and consider screening adults at least once for Lp(a) values.

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