Lp-PLA₂ Activity Test

Your standard lipid panel tells you how much cholesterol is circulating, and hs-CRP tells you whether your body has generalized inflammation. But neither one looks directly at what is happening inside the walls of your arteries. Lp-PLA2 (lipoprotein-associated phospholipase A2) fills that gap. It is an enzyme made by immune cells that have burrowed into arterial plaques, and its activity in your blood reflects how actively those plaques are being inflamed from the inside out.

What makes this marker distinctive is its specificity. Unlike CRP, which rises with infections, obesity, and dozens of other conditions, Lp-PLA2 activity is driven almost entirely by what is happening in your blood vessels. When a collaborative analysis of 32 prospective studies tracked over 79,000 people, each incremental rise in Lp-PLA2 activity independently predicted heart attack, stroke, and death from vascular causes, even after accounting for every traditional risk factor.

What Lp-PLA2 Activity Actually Measures

About 80% of Lp-PLA2 in your blood rides on LDL particles, the same particles that drive plaque formation. When LDL gets trapped in your artery walls and becomes chemically damaged (oxidized), Lp-PLA2 cuts apart those damaged fats. The problem is that the fragments it generates, specifically a molecule called lysophosphatidylcholine and oxidized fatty acids, are themselves powerful triggers of inflammation. They attract more immune cells, damage the inner lining of your arteries, and weaken the fibrous cap that keeps a plaque from rupturing.

This is why Lp-PLA2 has been found concentrated in the most dangerous type of plaques: the thin-capped, rupture-prone lesions that cause sudden heart attacks. The enzyme is not just a bystander. It is actively generating the chemical signals that make a plaque unstable.

A Marker, Not a Cause

There is an important distinction to understand before you interpret your results. Despite strong associations between Lp-PLA2 and cardiovascular events, randomized trials of darapladib, a drug designed specifically to block this enzyme, failed to reduce heart attacks or strokes in patients with stable coronary disease or after acute coronary syndrome. Genetic studies of people born with inactive versions of this enzyme have also produced mixed results. This means Lp-PLA2 is almost certainly a reliable signal of dangerous arterial inflammation, but directly blocking it does not fix the problem. Think of it as a smoke detector rather than the fire itself.

That distinction matters for how you use your results. An elevated Lp-PLA2 activity level tells you that active, vascular-specific inflammation is present and that your cardiovascular risk is higher than standard tests alone suggest. The appropriate response is to address the upstream drivers of that inflammation, primarily atherogenic lipoproteins, rather than to target Lp-PLA2 itself.

Heart Disease Risk

The strongest evidence linking Lp-PLA2 activity to disease comes from cardiovascular studies. In the largest pooled analysis, covering 32 prospective studies and over 79,000 participants, each one-standard-deviation increase in Lp-PLA2 activity was associated with a 10% higher risk of coronary heart disease, a 16% higher risk of dying from vascular causes, and a 10% higher risk of dying from non-vascular causes, after full adjustment for traditional risk factors.

Individual cohort studies paint a consistent picture. The relationship between Lp-PLA2 activity and heart disease risk appears to start at levels well below any obvious threshold.

What this means for you: the risk signal from Lp-PLA2 activity is not dramatic for any single jump in level, but it is remarkably consistent, and it persists after adjusting for cholesterol, blood pressure, smoking, and diabetes. If your Lp-PLA2 activity is elevated, your arteries are inflamed beyond what your cholesterol numbers alone would predict.

Stroke Risk

Lp-PLA2 activity also predicts ischemic stroke, the type caused by a blood clot blocking an artery to the brain. A meta-analysis of 22 studies covering over 157,000 participants found that each one-standard-deviation increase in activity raised ischemic stroke risk by 8%. Comparing the highest to the lowest category of activity, the risk of ischemic stroke was 29% higher.

The combination of elevated Lp-PLA2 and elevated hs-CRP appears particularly potent for stroke prediction. In the ARIC study of middle-aged men and women, those with both markers elevated had more than 11 times the risk of ischemic stroke compared to those with both markers low.

Synergy with CRP

One of the most practical aspects of Lp-PLA2 testing is how it pairs with hs-CRP. These two markers measure different types of inflammation through unrelated biological pathways, and they are statistically independent of each other (their correlation is close to zero). CRP reflects whole-body inflammation and is heavily influenced by body fat. Lp-PLA2 reflects inflammation specifically inside artery walls and is not affected by obesity.

When both are elevated together, the combined risk is substantially greater than either marker alone. AACE guidelines recommend that when both Lp-PLA2 and hs-CRP are high, LDL cholesterol targets should be lowered by an additional 30 mg/dL beyond standard goals. This makes the pairing of Lp-PLA2 activity with hs-CRP one of the most actionable two-test combinations in cardiovascular prevention.

Diabetes and Metabolic Risk

Lp-PLA2 activity is elevated in people with metabolic syndrome and shows links to insulin resistance. In the Cardiovascular Health Study, higher Lp-PLA2 activity predicted the future development of type 2 diabetes in older adults. Diabetes status also amplifies the cardiovascular risk signal: people with poorly controlled diabetes (HbA1c at 6.5% or higher) and elevated Lp-PLA2 activity carried the highest risk of major coronary events.

Reference Ranges

Lp-PLA2 activity values depend heavily on which assay your lab uses. The two main methods produce very different numbers: colorimetric assays (the CAM method, used by most commercial labs) report values roughly 3.5 times higher than radiometric assays. Always compare your results within the same lab over time, not against numbers from a different source.

Men typically have activity levels about 10 to 15% higher than women, and levels tend to be roughly 15% higher in white individuals compared to Black or Hispanic individuals. These demographic differences mean that a single universal cutpoint may not apply equally across populations.

These tiers are drawn from published population data including the Lp-PLA2 Studies Collaboration (mean 151 nmol/min/mL) and the Dallas Heart Study (mean 146 nmol/min/mL). Your lab may use different assays and cutpoints. The relationship between Lp-PLA2 activity and cardiovascular risk is continuous and roughly log-linear, meaning there is no single threshold that cleanly separates safe from dangerous. Compare your results within the same lab over time for the most meaningful trend.

Tracking Your Trend

The good news about Lp-PLA2 activity is that it is one of the most stable and reproducible cardiovascular biomarkers available. More than 90% of the total variability in Lp-PLA2 activity comes from differences between people, not from fluctuations within the same person over time. The day-to-day variation within one individual is under 4%, and fasting, time of day, and meals do not meaningfully shift the result. A change of more than 17% from one measurement to the next is considered clinically significant, meaning that anything below that threshold is likely just normal analytical noise.

This stability has a practical benefit: a single reading is reliable for initial risk assessment. But it also means that serial measurements are a powerful way to track whether your interventions are working. Statins, for example, reduce Lp-PLA2 activity by 20 to 35%. If you start a statin or make significant dietary changes, retesting in 3 to 6 months will show whether that inflammatory signal in your arteries is actually responding. After that, annual monitoring gives you a reliable trend line. Your own trajectory matters more than any single population-based cutpoint.

When Results Can Be Misleading

Lp-PLA2 behaves differently from most inflammatory markers during acute illness, and this can trip up interpretation if you are not aware of it. After a heart attack or stroke, Lp-PLA2 mass and activity both drop sharply (by roughly 30 to 35%), even as CRP spikes upward. Measurements taken within days to weeks of an acute vascular event will underestimate your true baseline. If you have recently been hospitalized for a heart attack or stroke, wait until you are fully recovered and clinically stable before testing.

Chronic kidney disease is the other major confounder. Lp-PLA2 activity is significantly elevated in people with advanced kidney disease and in those on dialysis, independent of their cardiovascular risk. If your kidney function is significantly impaired, an elevated Lp-PLA2 may partly reflect kidney dysfunction rather than arterial inflammation.

Statin therapy reliably lowers Lp-PLA2 activity by 20 to 35%, primarily because statins reduce the LDL particles that carry most of the enzyme. This is not a false result; it reflects a genuine reduction in the inflammatory substrate. But it means that your on-treatment Lp-PLA2 value does not represent your untreated vascular inflammatory burden. If you start or stop a statin, expect your Lp-PLA2 to shift accordingly, and interpret changes against your current medication regimen.