Lp-PLA2 activity is a blood test that measures how much of a specific enzyme, lipoprotein-associated phospholipase A2, is actively working in your bloodstream. This enzyme is a marker of inflammation happening inside your artery walls, and elevated levels signal a higher risk of heart attack and stroke. An activity level above 123 nmol/min/mL is considered high risk.
Unlike general inflammation markers that can spike from a cold or a twisted ankle, Lp-PLA2 is produced by immune cells embedded in arterial plaques themselves. That specificity is what makes it useful: it points directly at the kind of inflammation that leads to cardiovascular events.
What the Enzyme Actually Does
Lp-PLA2 rides through your bloodstream attached to LDL cholesterol (the “bad” cholesterol). When LDL particles become trapped in artery walls and oxidize, Lp-PLA2 breaks down the oxidized fats on those particles. That sounds like cleanup, but the byproducts of that breakdown are the problem. The reaction releases compounds called lysophosphatidylcholine and oxidized fatty acids, both of which trigger a chain of inflammatory damage inside the artery wall.
These byproducts attract more immune cells to the area, damage the inner lining of the artery, and contribute to the buildup of a fatty, unstable core inside arterial plaques. Over time, the inflammation and cell death caused by this cycle can weaken the fibrous cap that holds a plaque together. When that cap becomes thin enough to rupture, it triggers a blood clot, which is the mechanism behind most heart attacks and many strokes.
So while Lp-PLA2 has a normal role in breaking down certain inflammatory molecules elsewhere in the body, its activity inside artery walls is actively destructive. The more of it circulating and working on oxidized LDL, the more pro-inflammatory damage accumulates.
How It Differs From CRP
If you’ve had cardiovascular risk screening before, you may have had a high-sensitivity CRP (hs-CRP) test. CRP is made in the liver and rises in response to inflammation anywhere in the body: an infection, arthritis, even stress. Lp-PLA2 is different because it’s produced by macrophages and foam cells inside vulnerable arterial plaques. That makes it a specific marker of vascular inflammation rather than a general one.
The two tests don’t closely track each other. A person can have normal CRP but elevated Lp-PLA2, or vice versa. Research shows that Lp-PLA2 predicts cardiovascular events independently of CRP, and when both markers are elevated together, the risk climbs further. This is why some clinicians order both: they capture different dimensions of inflammatory risk.
What Elevated Levels Mean for Risk
A large collaborative analysis pooling 32 prospective studies, published in The Lancet, found that each standard-deviation increase in Lp-PLA2 activity raised the risk of coronary heart disease by about 10% after adjusting for conventional risk factors like cholesterol, blood pressure, and smoking. For deaths from vascular causes, the increase was 16% per standard deviation. The association with ischemic stroke was smaller (8%) and not statistically definitive, though Lp-PLA2 mass (a slightly different measurement) showed a clearer 14% increase in stroke risk.
These numbers represent population-level averages, so your individual risk depends on the full picture of your health. But the key takeaway is that Lp-PLA2 activity adds information beyond what standard cholesterol panels and blood pressure readings tell you. It’s most useful for people who fall into a gray zone on traditional risk calculators, where the decision to intensify treatment isn’t obvious.
Who Should Get Tested
A consensus panel building on guidelines from the Adult Treatment Panel III and the American Heart Association recommended Lp-PLA2 testing as an add-on for patients at moderate or high 10-year cardiovascular risk. The idea is straightforward: if your risk is borderline based on traditional factors, an elevated Lp-PLA2 level can justify bumping you into a higher risk category, which may change treatment decisions.
For someone already classified as high risk, an elevated result could push the classification to very high risk, prompting more aggressive cholesterol-lowering targets. The panel suggested considering a reduction in LDL cholesterol targets by 30 mg/dL in patients with high Lp-PLA2 levels. Importantly, the panel noted that Lp-PLA2 itself is not yet a direct treatment target. It’s used for decision-making, not as something clinicians try to lower on its own.
Understanding Your Results
The standard commercial test for this enzyme is the PLAC test. Cleveland Clinic Laboratories defines the reference ranges simply:
- Goal (optimal): 123 nmol/min/mL or below
- High risk: above 123 nmol/min/mL
No fasting is required before the blood draw, which makes it easy to add to routine lab work. Samples that are hemolyzed (red blood cells broken during collection) or visibly milky from high triglycerides will be rejected and need to be redrawn.
It’s worth knowing that the test measures activity (how much the enzyme is doing) rather than just mass (how much enzyme protein is present). Both measurements exist, and they sometimes tell slightly different stories. Activity is the more commonly ordered version and reflects the enzyme’s functional impact on oxidized LDL in real time.
How Statins Affect Lp-PLA2
A 2024 meta-analysis of 10 randomized controlled trials found that statin therapy significantly reduced both Lp-PLA2 mass and activity. Activity dropped by an average of about 39 nmol/min/mL compared to placebo, while mass dropped by roughly 44 ng/mL. This makes sense biologically: statins lower LDL cholesterol, which means fewer LDL particles for the enzyme to attach to and fewer oxidized phospholipids for it to act on.
This reduction happens as a secondary benefit of statin therapy, not because statins directly inhibit the enzyme. A dedicated Lp-PLA2 inhibitor drug called darapladib was tested in large clinical trials but failed to reduce cardiovascular events, which is part of why guidelines recommend using Lp-PLA2 as a risk marker rather than a treatment target. The most effective way to bring levels down remains lowering LDL cholesterol through medication and lifestyle changes like improved diet, regular exercise, and weight management.