Lp-PLA2 Activity
How active an enzyme is that travels mostly on LDL particles and is found in artery plaque. Higher activity is linked to higher heart risk, but it is an add-on test.
AI-drafted. Awaiting verificationAlso called Lp-PLA2, PAF-AHLOINC 86951-1
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What it is
Lp-PLA2 (lipoprotein-associated phospholipase A2) is an enzyme made by inflammatory cells. It circulates mostly attached to LDL particles, with a smaller share on HDL, and it is found in higher amounts in advanced plaque in artery walls. This test measures how active the enzyme is, in nmol/min/mL, not how much of it there is. A separate test, Lp-PLA2 mass, measures the amount, so the two numbers can't be swapped.
Why it matters
In a pooled analysis of 32 studies and 79,036 people, higher Lp-PLA2 activity was linked to a somewhat higher chance of coronary heart disease, about 10% higher for each standard deviation, after adjusting for usual risk factors. That is similar in size to the link with non-HDL cholesterol or blood pressure, and part of it runs through cholesterol, because activity rises with LDL, non-HDL cholesterol and apoB. Two large trials of a drug that blocks the enzyme did not lower the main heart event rates. So Lp-PLA2 is a risk marker, not a proven target. Labcorp describes its test as an aid for predicting heart disease risk in people with no history of heart events.
If it’s low
Lower activity is the direction both labs treat as lower risk. A low result is not a concern on its own.
Common causes
- Lower LDL and non-HDL cholesterol
- Higher HDL cholesterol
- Female sex. Activity is lower in women than in men on average
If it’s high
Higher activity is linked to a higher chance of heart attack and stroke over time, mostly in studies of large groups. It can't tell you whether you have heart disease. Because activity rises along with LDL cholesterol, a high result often reflects high LDL or non-HDL cholesterol. Your clinician can put your result in context.
Common causes
- High LDL cholesterol, non-HDL cholesterol or apoB, which rise together with Lp-PLA2 activity
- High triglycerides
- Low HDL cholesterol
- Male sex. Activity is higher in men than in women on average
- A different assay, since Quest and Labcorp use different methods and cutoffs
What can help
- Ask your clinician how your LDL cholesterol, non-HDL cholesterol and apoB look, since they move with this result
- Eat more vegetables, fruit, whole grains and nuts, and less saturated fat, and be active most days. These habits help cholesterol in general
- Ask whether this test would change anything about your care
Usual ranges
What labs print as the reference range, by who was tested. Ranges differ a little between labs, so the range on your own report is the one your result is judged against.
For adults: up to 123 nmol/min/mL. Source: Quest Diagnostics (via Fullscript).
- Adults (this one applies)up to 123 nmol/min/mL
Quest Cardio IQ Lp-PLA2 activity risk groups (for whole-number results)
- Optimalbelow 124 nmol/min/mL
- High124 and above nmol/min/mL
Labcorp PLAC test Lp-PLA2 activity risk groups
- Reduced riskbelow 225 nmol/min/mL
- Increased risk225 and above nmol/min/mL
What can affect your result
- Lab and assay: Quest and Labcorp use different methods and cutoffs, so compare only results from the same lab
- Cholesterol levels: activity rises with LDL, non-HDL cholesterol, apoB and triglycerides, and falls with HDL cholesterol
- Sex: higher in men than in women on average
- Age, blood pressure, body weight, smoking and CRP show only a weak or no link with activity in pooled studies
- Fasting: Labcorp says it is not required, and Quest suggests 8 hours but says it is not required
- Labcorp rejects samples that are hemolyzed, very turbid or clotted.
- Different labs use different assays and cutoffs (Quest 123 nmol/min/mL, Labcorp 225), so only compare results from the same lab.
- Activity and mass are different tests. Lp-PLA2 mass is reported in ng/mL and can't be converted to or from activity.
No published timeline. Activity rises and falls with LDL, non-HDL cholesterol and apoB, so it may shift as they do over weeks to months.
When to talk to a clinician
No Lp-PLA2 value is an emergency on its own. Bring a result above your lab's range to your next routine visit, along with your cholesterol results, especially if you have diabetes, high blood pressure, a family history of early heart disease or you smoke. If you have chest pain or pressure, trouble breathing, or signs of a stroke such as face drooping, arm weakness or trouble speaking, call 911 or your local emergency number, whatever your results are.
Questions you could ask
- Which lab's range should I use for this test?
- Is this test useful for me, or would my standard lipid panel and apoB be enough?
- Is my result high because of my cholesterol numbers, and which of those should we follow?
- Would this result change my care?
- Should we look more closely at my LDL cholesterol, non-HDL cholesterol or apoB?
Questions people ask
Why do Quest and Labcorp use different cutoffs?
They use different assays, and each lab sets its own risk cutoff. Quest uses 123 nmol/min/mL and Labcorp uses 225. The numbers can't be swapped, so compare your result with the range printed on your own report.
Is there a treatment that lowers Lp-PLA2?
A drug that blocks the enzyme, darapladib, was tested in two large trials (about 15,800 and 13,000 people) and did not lower the main heart event rates. Because Lp-PLA2 activity moves with LDL and non-HDL cholesterol, your clinician is more likely to focus on those.
Do I need to fast for this test?
Probably not. Labcorp says fasting is not required for this test, and Quest suggests fasting for 8 hours but says it is not required. Follow any instructions your lab gives you, especially if other tests are drawn at the same time.
Show the science and sources
For clinicians and researchers
Lp-PLA2 (platelet-activating factor acetylhydrolase) is a calcium-independent phospholipase A2 produced by macrophages and other inflammatory cells. It circulates mainly bound to LDL and, to a lesser extent, HDL, hydrolyzes oxidized phospholipids to lysophosphatidylcholine and oxidized free fatty acids, and is enriched in advanced lesions. Activity assays (LOINC 86951-1, nmol/min/mL) measure substrate hydrolysis, while mass assays (LOINC 39804-0) measure protein. Activity and mass correlate at r = 0.51. Labcorp's PLAC test is a spectrophotometric enzymatic assay with a cutoff of 225 nmol/min/mL (reduced risk below 225, increased risk 225 or above, printed as a 0-224 interval), and Quest's Cardio IQ assay runs on an automated chemistry platform with a cutoff of 123 nmol/min/mL (optimal at 123 or below, high above), so values are not transferable. In the Lp-PLA2 Studies Collaboration (32 prospective studies, 79,036 participants, 17,722 outcomes), the risk ratio for coronary heart disease per 1 SD higher activity was 1.10 (95% CI 1.05-1.16), versus 1.10 for non-HDL cholesterol and 1.10 for systolic blood pressure, and the vascular associations depended at least partly on lipids. Activity correlated with non-HDL cholesterol (r = 0.49), direct LDL-C (0.48), apoB (0.45) and triglycerides (0.22), inversely with HDL-C (-0.24), was higher in men, and showed weak or no association with age, blood pressure, BMI, smoking, CRP, fibrinogen or leukocyte count. Within-person variability could not be pooled reliably. Darapladib, a selective Lp-PLA2 inhibitor, did not reduce the primary composite end point in STABILITY (15,828 patients with stable coronary disease; HR 0.94, 95% CI 0.85-1.03) or major coronary events in SOLID-TIMI 52 (13,026 patients after acute coronary syndrome; HR 1.00, 0.91-1.09). Labcorp's PLAC test is intended as an aid in predicting coronary heart disease risk in people with no prior cardiovascular events.
LOINC 86951-1 (primary). Specimen: serum-or-plasma.
Sources
- Lp-PLA2 Activity, Quest Diagnostics (reference range as listed by Fullscript), Quest Diagnostics (via Fullscript)
- Lipoprotein-Associated Phospholipase A2 Activity (PLAC test, test 123283), Labcorp
- Lp-PLA2 Activity, sample patient report (test 123283), Labcorp (2017)
- Lipoprotein-associated phospholipase A2 and risk of coronary disease, stroke, and mortality: collaborative analysis of 32 prospective studies, The Lancet (2010)
- Darapladib for preventing ischemic events in stable coronary heart disease (STABILITY), New England Journal of Medicine (2014)
- Effect of darapladib on major coronary events after an acute coronary syndrome: the SOLID-TIMI 52 randomized clinical trial, JAMA (2014)
- Blood Cholesterol: Treatment (lifestyle changes), National Heart, Lung, and Blood Institute
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