Lipoprotein(a): The Inherited Cardiovascular Risk Factor Most Adults Have Never Tested

A patient walks into a preventive cardiology clinic with a textbook-clean profile. LDL cholesterol of 95 mg/dL on a moderate-dose statin. Blood pressure 118/76. Hemoglobin A1c of 5.4. Never smoked. Walks 8,000 steps a day. By every metric on a standard lipid panel and most cardiovascular risk calculators, this is a low-risk patient. Two years later, at 51, she has a heart attack.

Cases like this are not as rare as the standard risk framework suggests. A meaningful fraction of premature coronary events occur in adults whose conventional risk factors are well controlled. One of the most common explanations — frequently missed because almost no one is tested for it — is elevated lipoprotein(a), commonly written as Lp(a) and pronounced "L-P-little-a."

What Lp(a) Actually Is

Lipoprotein(a) is a low-density lipoprotein particle with an additional protein, apolipoprotein(a), covalently attached to its apolipoprotein B-100 backbone. The apo(a) component is structurally similar to plasminogen, the precursor to the body's main fibrin-dissolving enzyme. This dual identity is what makes Lp(a) biologically dangerous. It carries cholesterol into the arterial wall like LDL, and it interferes with the body's ability to break down clots like plasminogen, while also promoting valvular calcification and chronic inflammation.

In short, Lp(a) is atherogenic, prothrombotic, and pro-inflammatory in a single particle. Most other cardiovascular risk markers do one of those three things. Lp(a) does all three.

The trait is overwhelmingly genetic. Roughly 70 to 90% of an individual's Lp(a) level is determined by variation in the LPA gene, which encodes apo(a). Levels are essentially set in childhood, change only modestly with diet or exercise, and remain stable across decades. This stability is why a single lifetime measurement is generally sufficient — a striking exception in a field where most lipid markers require ongoing monitoring.

How Common Is "High"?

The European Atherosclerosis Society 2022 consensus statement, led by Kronenberg and colleagues, summarized the population data clearly. Approximately 20 to 25% of adults globally carry Lp(a) levels above the threshold typically used to define increased cardiovascular risk — most commonly 50 mg/dL or 125 nmol/L. The distribution is heavily right-skewed and varies by ancestry. Adults of South Asian and African ancestry tend to carry higher mean Lp(a) levels than adults of European ancestry, though high levels occur across every population.

That prevalence figure deserves to be stated more loudly. One in four to five adults carries a genetically elevated, lifelong cardiovascular risk factor that almost no standard risk calculator captures and almost no routine lipid panel measures. Compared with the public attention given to LDL cholesterol — which is roughly equally prevalent at modestly elevated levels — Lp(a) is dramatically underdiagnosed.

The Evidence That Lp(a) Causes Disease

Association is not causation. The strongest evidence that Lp(a) directly causes cardiovascular events comes from genetic studies in which nature has effectively run the trial.

Clarke and colleagues (NEJM, 2009) examined LPA gene variants in over 3,000 cases of coronary disease and 3,000 controls. Variants that produced higher Lp(a) levels were associated with proportionally higher coronary disease risk. Because gene variants are randomized at conception, this design — known as Mendelian randomization — provides causal rather than correlational evidence. The signal has since been replicated across multiple populations and biobank-scale datasets.

Kamstrup and colleagues (Circulation, 2008), working in the Copenhagen City Heart Study, found that adults with Lp(a) levels above the 95th percentile had roughly three to four times the risk of myocardial infarction compared with adults below the 22nd percentile. The relationship was continuous and graded across the full distribution, not limited to extreme values.

Subsequent work has expanded the picture. Elevated Lp(a) is now recognized as a causal driver of:

• Premature coronary artery disease, particularly in adults under 55
• Calcific aortic valve stenosis, where Lp(a) accumulation in the valve leaflet appears to be a primary mechanism rather than a secondary marker
• Ischemic stroke, with effect sizes smaller than for coronary disease but still significant
• Recurrent cardiovascular events, including after revascularization in patients already on intensive statin therapy

The American Heart Association 2022 scientific statement on Lp(a) reviewed this evidence and concluded that Lp(a) meets the standard criteria for a causal cardiovascular risk factor.

Why It Has Been Largely Ignored Until Recently

If Lp(a) is so common and so clearly causal, why has it taken until the 2020s for it to enter routine preventive practice? Three reasons.

First, there was no specific therapy for most of the last three decades. Statins, the dominant preventive cardiology tool since the 1990s, do not lower Lp(a) and may modestly raise it. PCSK9 inhibitors lower Lp(a) by roughly 25%, but they are expensive and were not specifically licensed for Lp(a) reduction. Without a treatment to recommend, the case for measurement was clinically weaker.

Second, assay standardization has been a long-running problem. Lp(a) levels were historically reported in mg/dL using mass-based assays that varied by laboratory and were sensitive to apo(a) isoform size. Newer assays report in nmol/L using particle-counting methods that are more reproducible. The shift has been gradual, and confusion about units persists in clinical practice.

Third, traditional risk calculators do not include Lp(a). The Pooled Cohort Equations, Framingham, and even the newer 2024 PREVENT equations from the AHA estimate cardiovascular risk without an Lp(a) input. A patient whose entire excess risk is driven by Lp(a) appears average on these tools, and clinicians who rely solely on the calculator output miss the elevated risk entirely.

What Changed: The siRNA and ASO Pipeline

The therapeutic gap is closing. A class of RNA-targeted drugs — antisense oligonucleotides (ASOs) and small interfering RNAs (siRNAs) — selectively reduce hepatic production of apo(a) and have shown Lp(a) reductions of 80 to 98% in phase 2 trials. O'Donoghue and colleagues (NEJM, 2022) reported that olpasiran, a siRNA, produced sustained Lp(a) reductions exceeding 95% with quarterly subcutaneous dosing. Pelacarsen, an ASO, has produced similar reductions with monthly dosing.

The phase 3 cardiovascular outcomes trials for these agents — HORIZON for pelacarsen and OCEAN(a) for olpasiran — are now reading out in stages, with full results expected in 2026 to 2027. They are the trials that will determine whether lowering Lp(a) pharmacologically reduces cardiovascular events. If the answer is yes, Lp(a) screening will move from a niche preventive practice to a mainstream one within a clinical generation.

That timeline matters for a practical reason. Patients identified now — before the outcomes data lands — can be optimized on every other modifiable risk factor, can have their family members screened, and can be first in line for therapy if and when it is approved. Knowledge precedes therapy by years; testing now is not premature.

Who Should Be Tested

Major guidelines have converged on a permissive approach. The European Society of Cardiology now recommends measuring Lp(a) at least once in every adult's lifetime, framing the test similarly to a one-time genetic risk assessment. The U.S. picture is more fragmented, but the National Lipid Association and AHA both endorse Lp(a) measurement in:

• Anyone with a personal history of premature cardiovascular disease (men under 55, women under 65)
• Anyone with a first-degree relative with premature cardiovascular disease
• Anyone with a family history of elevated Lp(a)
• Patients with familial hypercholesterolemia
• Patients with recurrent cardiovascular events despite well-controlled LDL
• Patients with calcific aortic stenosis, especially before age 65

Pragmatically, the case for universal one-time measurement is strong. The test costs roughly 30 to 100 USD depending on insurance and laboratory, requires no fasting, and the result follows the patient for life. Compared with the cost of a missed myocardial infarction in a 50-year-old with otherwise pristine numbers, the math is not close.

What Elevated Lp(a) Actually Means in Practice

A patient who tests at, say, 180 nmol/L — well above the 125 nmol/L threshold — should not panic. Elevated Lp(a) raises risk; it does not guarantee an event. The clinical response is to intensify everything else that is modifiable.

LDL targets become more aggressive. A patient who would otherwise be content with an LDL of 100 mg/dL on lifestyle alone often warrants statin therapy aimed at LDL below 70 mg/dL when Lp(a) is high. Blood pressure and ApoB targets tighten correspondingly. Smoking, already non-negotiable in cardiovascular prevention, becomes more so — the multiplicative interaction between smoking and elevated Lp(a) is particularly steep.

Family screening is the second pillar. Because Lp(a) is inherited in a roughly Mendelian pattern, a positive result in an index patient meaningfully shifts the pretest probability for first-degree relatives. Adult children, siblings, and parents should be offered testing when an index case is identified.

For valvular disease, periodic echocardiography starting in late middle age is reasonable in patients with markedly elevated Lp(a) who are otherwise asymptomatic, given the established link to aortic stenosis and the typically slow rate of valve calcification.

The Limits of What We Know

Several questions remain genuinely open. The optimal threshold for treatment intensification is debated; values from 30 to 50 mg/dL (roughly 75 to 125 nmol/L) appear in different guidelines. Whether very mild elevation in an otherwise low-risk individual changes management is unclear. Whether Lp(a) reduction by 80% or more produces proportional event reduction will be answered by the ongoing trials, but the assumption — strong as it is — has not yet been confirmed.

What is no longer in question is that Lp(a) is real, measurable, common, and causal. The evidence base for those four claims has been settled for years. The clinical infrastructure has been the bottleneck.

A Single Test, A Lifetime of Useful Information

Most adults will never have an Lp(a) measurement ordered for them by a primary care physician. The default lipid panel does not include it, the standard risk calculators do not require it, and clinical inertia favors continuing to do what was done last year. Patients who want to know their level generally have to ask for it specifically.

The test itself is unremarkable. A standard blood draw, processed by any major reference laboratory, reported within 48 hours. The result is a number that will not meaningfully change for the rest of the patient's life. If it is low, the patient gains useful reassurance. If it is high, the patient gains a piece of information that reshapes the conversation about lifelong cardiovascular risk and triggers screening for the family members who share the gene.

Few preventive tests offer that ratio of one-time effort to lifetime informational value. Lp(a) is one of them, and most adults still have not had it run.

James Whitfield is the Preventive Care Editor at HealthKoLab. He holds an MPH from Johns Hopkins Bloomberg School of Public Health with a concentration in cardiovascular epidemiology.