Lp-PLA2 (the PLAC Test): What It Means for Your Heart

TL;DR: Lp-PLA2, measured by the PLAC test, is an enzyme that rides on your LDL and stirs up inflammation inside artery plaque, so it is marketed as a marker of vascular inflammation. A high level does carry a modest heart-risk signal, about 10% higher coronary risk per standard deviation across large studies. But it is one of the clearest examples of a marker that is not a treatment target: a drug built to lower Lp-PLA2 was tested in almost 29,000 people across two large trials, lowered the enzyme, and did not reduce heart attacks, strokes, or cardiovascular deaths, and people born with genetically low Lp-PLA2 do not get less heart disease. There is nothing to prescribe against the number. A high result is a reason to double down on the levers that do matter, lowering ApoB and LDL, blood pressure, not smoking, and metabolic health, rather than to chase the enzyme itself.

If a high Lp-PLA2, often labeled the PLAC test, turned up on an advanced lipid or cardiac panel, this page explains what it means and, more usefully, what it does not. Lp-PLA2 has an unusual distinction among heart markers: its story is close to settled, because a drug was built to lower it and put through two large trials. Knowing how those trials turned out tells you almost everything you need about how to read the number.

What is Lp-PLA2, and why is it called a vascular inflammation marker?

Lp-PLA2 stands for lipoprotein-associated phospholipase A2, sometimes labeled PAF-AH on a lab report, and it is an enzyme that travels through the blood attached mostly to LDL, the cholesterol particle that drives plaque. Inside the artery wall, macrophages, the immune cells that pile into a growing plaque, produce Lp-PLA2, and the enzyme breaks down oxidized fats there into products that fuel inflammation.⁶ Because it is generated within the vessel wall and is less swayed by everyday infections than a general inflammation marker, it is sold as a test of vascular inflammation, the inflammation specific to arteries.

That framing is partly fair and partly marketing. Lp-PLA2 is more artery-focused than C-reactive protein, which rises with any infection or inflammation anywhere in the body. But the vascular-specific label is a relative claim rather than an absolute one. Because Lp-PLA2 rides on LDL, its risk signal partly reflects your cholesterol, and in the largest study it also tracked with non-vascular deaths, so it is not a pure readout of artery inflammation.

Does a high Lp-PLA2 predict heart disease?

Yes, but the signal is modest. In the largest pooled analysis, combining 32 studies and about 79,000 people, higher Lp-PLA2 was linked to more coronary heart disease, with roughly a 10% increase in risk per standard deviation once other risk factors were accounted for, an effect similar in size to a single conventional risk factor like non-HDL cholesterol or blood pressure.¹ The association with stroke was weaker and lost significance after adjustment, and the signal attenuated overall once researchers accounted for the cholesterol Lp-PLA2 travels with.

The PLAC test is cleared by the FDA to help assess coronary heart-disease risk, and an older version of the test also carried a stroke indication. But Lp-PLA2 is not part of the standard risk calculators, and when the cholesterol guidelines chose extra markers to refine risk, they picked high-sensitivity CRP, Lp(a), and ApoB rather than Lp-PLA2.⁷ It adds little once the standard factors are known.

The key evidence: a drug lowered it and nothing happened

Here is what sets Lp-PLA2 apart from most markers, and what should shape how you read it. The idea that Lp-PLA2 drives heart disease was not left as a theory; it was tested with a drug. A selective Lp-PLA2 inhibitor called darapladib was developed and run through two large randomized trials.

In the first, involving 15,828 patients with stable coronary disease, darapladib lowered Lp-PLA2 but did not significantly reduce the combined rate of cardiovascular death, heart attack, and stroke.² In the second, involving 13,026 patients just after a heart attack or unstable angina, it again failed to reduce major coronary events, with no benefit at all.³ Across nearly 29,000 people, a drug that clearly lowered the enzyme prevented no net events.

Genetics tell the same story. People who inherit gene variants that lower their Lp-PLA2 activity, including variants that cut it substantially, do not have less heart disease.⁴⁵ When both a drug trial and a natural genetic experiment point the same way, the conclusion is hard to escape: Lp-PLA2 is a marker that reflects atherosclerosis rather than a cause you can treat by lowering the number.

Is there a treatment to lower Lp-PLA2?

No, and that follows directly from the trials. Darapladib was never approved, because it did not work, and no other drug targets Lp-PLA2. Statins do lower Lp-PLA2, but only as a byproduct of lowering LDL cholesterol; the benefit comes from the LDL reduction rather than from any effect on the enzyme itself. In practical terms, there is nothing to prescribe against a high Lp-PLA2, and no reason to want one, because moving the number on its own would not move your risk.

What counts as a high Lp-PLA2?

The answer depends on which version of the test was run, which is a detail to confirm. The activity assay, the one most labs now use, reports results in enzyme units, with a common cutoff around 225 for higher risk, though the evidence for a single threshold is weak and some data support different cutoffs for men and women. The older mass assay reports in different units, so its numbers cannot be compared with the activity assay. Whichever was measured, Lp-PLA2 rises with higher LDL, more atherosclerosis, excess weight, and higher blood pressure, which is part of why it overlaps so much with the cholesterol and risk factors you already track.

How to respond to a high Lp-PLA2

Because Lp-PLA2 reflects the atherosclerosis and cholesterol it travels with, the productive response is to treat those drivers rather than the enzyme. The highest-leverage move is to lower your ApoB, the count of harmful cholesterol particles that LDL stands in for, and doing so with a statin or similar drug lowers Lp-PLA2 as a side effect anyway. After that come the other proven levers: blood pressure, not smoking, and metabolic health. If a high Lp-PLA2 prompts you to check the markers that do change management, like Lp(a) or a coronary calcium score, it will have done something useful.

Where Lp-PLA2 sits in the hierarchy of heart markers is a rung below the ones that count. ApoB, Lp(a), and blood pressure are causal and actionable, the main event. High-sensitivity CRP is the inflammation marker the guidelines endorse. Lp-PLA2 is a roughly comparable inflammatory marker with a touch more artery focus, but with less guideline standing, less added value, and, thanks to the failed trials, the clearest proof of any of them that lowering it does nothing on its own.

How Fishtown Medicine reads Lp-PLA2 in Philadelphia

We treat Lp-PLA2 as a minor supporting character rather than a headline. When a patient brings us a high PLAC test from an outside panel, our first move is to reassure them about what the trials showed: a drug that lowered this enzyme did not prevent heart attacks, so there is nothing to chase here. Then we put the result to work the only way it can help, as one more reason to be thorough about the levers that matter.

That means looking hard at ApoB and LDL and treating them to target, checking Lp(a) once, managing blood pressure, and addressing metabolic health, because a high Lp-PLA2 usually means atherosclerosis deserves attention, even though the enzyme itself is not the thing to treat. When it helps to see the arteries directly, a coronary calcium score often tells us more than another inflammatory marker. Whether you are in Fishtown or Cherry Hill, the goal is to spend your effort where it changes outcomes.

Guidance from the Clinic

"When a patient shows me a high Lp-PLA2 and asks how we lower it, I get to share one of my favorite teaching stories in cardiology. A company built a drug to lower this exact enzyme, tested it in almost thirty thousand people, and it lowered the enzyme beautifully and did not reduce heart attacks or strokes, twice. On top of that, people born with naturally low Lp-PLA2 do not have healthier hearts. So my answer is that we do not treat the number, because the evidence says treating it would not help. What we do instead is use it as a prompt to get serious about ApoB, blood pressure, and the fundamentals, which is where the protection lives. It is a marker pointing at a problem rather than the problem itself."

Related at Fishtown Medicine

• High Fibrinogen: What It Means for Your Heart - the other inflammatory marker that predicts risk without a treatment
• ApoB and Heart Health - the causal, treatable lever a high Lp-PLA2 should send you toward
• High CRP: What an Elevated Inflammation Marker Means - the systemic inflammation marker Lp-PLA2 is often compared with
• Borderline Cholesterol, ApoB, and Lp(a) - reading the lipid markers that carry more weight
• The Advanced Tests Your Doctor Isn't Ordering - which markers earn a place on a panel

Scientific References

1. Thompson A, Gao P, Orfei L, et al; Lp-PLA2 Studies Collaboration. "Lipoprotein-associated phospholipase A2 and risk of coronary disease, stroke, and mortality: collaborative analysis of 32 prospective studies." The Lancet. 2010;375(9725):1536-1544.
2. White HD, Held C, Stewart R, et al; STABILITY Investigators. "Darapladib for preventing ischemic events in stable coronary heart disease." New England Journal of Medicine. 2014;370(18):1702-1711.
3. O'Donoghue ML, Braunwald E, White HD, et al; SOLID-TIMI 52 Investigators. "Effect of darapladib on major coronary events after an acute coronary syndrome: the SOLID-TIMI 52 randomized clinical trial." JAMA. 2014;312(10):1006-1015.
4. Casas JP, Ninio E, Panayiotou A, et al. "PLA2G7 genotype, lipoprotein-associated phospholipase A2 activity, and coronary heart disease risk in 10,494 cases and 15,624 controls of European ancestry." Circulation. 2010;121(21):2284-2293.
5. Polfus LM, Gibbs RA, Boerwinkle E, et al. "Coronary heart disease and genetic variants with low phospholipase A2 activity." New England Journal of Medicine. 2015;372(3):295-296.
6. Zalewski A, Macphee C. "Role of lipoprotein-associated phospholipase A2 in atherosclerosis: biology, epidemiology, and possible therapeutic target." Arteriosclerosis, Thrombosis, and Vascular Biology. 2005;25(5):923-931.
7. Grundy SM, Stone NJ, Bailey AL, et al. "2018 AHA/ACC/multisociety guideline on the management of blood cholesterol." Circulation. 2019;139(25):e1082-e1143.