Lipoprotein(a)

What is Lipoprotein(a)?

Lipoprotein(a) — abbreviated Lp(a) — is an LDL-like lipoprotein particle in which apolipoprotein(a) is covalently bound to ApoB-100 via a disulphide bridge. The apolipoprotein(a) molecule shares structural similarity with plasminogen — the protein that breaks down blood clots — but lacks its catalytic activity. This makes Lp(a) both atherogenic and prothrombotic: it promotes plaque formation and interferes with fibrinolysis, so the cumulative risk of heart attacks and strokes is greater than for a comparable LDL level without Lp(a) elevation. Lp(a) is reported in mg/dL or nmol/L; ESC/EAS guidelines prefer nmol/L because the conversion between the two units is not linear (particle size varies substantially due to a genetically determined number of kringle IV type 2 repeats). As a risk threshold, ESC/EAS uses 125 nmol/L (roughly 50 mg/dL) for markedly elevated risk, with any value above 75 nmol/L (roughly 30 mg/dL) considered moderately elevated. The level is roughly 90% genetically determined by the LPA gene and is stable throughout life for most people; a single measurement is therefore usually sufficient for cardiovascular risk stratification. Ethnicity strongly influences the distribution: people of African ancestry have on average twice the Lp(a) values of people of European ancestry; people of Asian ancestry have on average lower values. This is relevant when applying a single threshold across diverse populations.

Why is Lipoprotein(a) relevant?

Lp(a) is one of the few independent cardiovascular risk factors that falls entirely outside the standard lipid panel: a normal LDL, normal ApoB, and normal HDL do not rule out a markedly elevated Lp(a). Epidemiologically, the association is robust: each doubling of the Lp(a) concentration raises the relative risk of a coronary event by roughly 20–30%. At values > 125 nmol/L, the lifetime risk of atherosclerotic cardiovascular disease is substantial — comparable to that in heterozygous familial hypercholesterolaemia. Lp(a) is the most common cause of an 'unexplained' early heart attack in someone with an otherwise normal lipid profile: roughly 20–25% of the European population has Lp(a) above 75 nmol/L, and the skewed distribution means a small subgroup has very high values (> 250 nmol/L) with correspondingly high risk. Lp(a) also contributes to aortic valve stenosis — a pathology in which atherosclerotic plaque formation on the aortic valve leads to progressive narrowing. The clinical value of testing is twofold: first, it provides risk-stratification information that no other marker captures, allowing LDL and ApoB treatment targets to be set more precisely; second, it motivates family screening — Lp(a) is inherited autosomal co-dominantly, so children of a carrier carry on average half the parental level.

Lipoprotein(a) high or low — what it means

Lp(a) requires no fasting sample and is reliable at any time of day. It changes minimally with diet, weight, or lifestyle interventions — distinguishing it from LDL and triglycerides. Statins do not substantially lower Lp(a) and may even mildly raise it (on average 10–15%); PCSK9 inhibitors lower Lp(a) by 15–25%, though their primary effect is on LDL and ApoB. Specific Lp(a)-lowering therapies — including RNA interference agents and antisense oligonucleotides (olpasiran, pelacarsen, zerlasiran) — were in advanced Phase 3 studies in 2024–2025 and are expected to become available in coming years. With an elevated Lp(a), the clinical approach is two-pronged: on one hand, manage all other modifiable risk factors as aggressively as possible (LDL as low as possible, blood pressure controlled, no smoking, regular exercise), because Lp(a) and LDL/ApoB add to cardiovascular risk; on the other hand, depending on the overall risk profile, consider whether more intensive prevention (higher-intensity statin, PCSK9 inhibitor) is indicated. At Lp(a) > 125 nmol/L combined with existing ASCVD or familial hypercholesterolaemia, early intensive lipid lowering is standard in the ESC/EAS 2023 guidelines. An important reporting note: the unit makes a large difference. mg/dL and nmol/L are not directly interchangeable via a fixed factor (particle size varies per person due to the number of kringle repeats). Check which unit your laboratory reports and always compare values using the same unit. When a value is in mg/dL and the European nmol/L threshold of 125 nmol/L is being used, the rough approximation of 50 mg/dL is a conservative lower bound.

Educational information only — not medical advice. Consult a healthcare professional for clinical decisions.