Lipoprotein(a)
Overview
Lipoprotein(a), or Lp(a), measures the concentration of a low-density lipoprotein particle covalently bound to apolipoprotein(a), which structurally resembles plasminogen. Lp(a) promotes atherosclerosis by carrying cholesterol like LDL while inhibiting fibrinolysis through competitive binding to plasminogen receptors. Elevated Lp(a) levels, largely genetically determined, indicate increased risk for atherosclerotic cardiovascular disease, aortic stenosis, and thromboembolic events; low levels are not clinically significant. Clinically, Lp(a) testing identifies individuals with residual cardiovascular risk despite optimal LDL management and guides intensified preventive therapies.
Clinical Use Cases
- Risk stratification for atherosclerotic cardiovascular disease in patients with family history or premature events.
- Identifying residual risk in patients with optimally treated LDL cholesterol.
- Evaluating familial hypercholesterolemia and genetic dyslipidemias.
- Assessing risk for aortic valve calcification and stenosis.
Specimen Types
- Serum.
- Plasma (EDTA preferred; avoid heparin plasma).
Measurement Methods
- Immunoassay (turbidimetric or nephelometric) reporting Lp(a) cholesterol or particle concentration.
- Agarose gel electrophoresis with LDL-cholesterol subtraction (legacy method).
- Liquid chromatography-mass spectrometry for isoform-specific measurement.
Test Preparation and Influencing Factors
- Non-fasting sample acceptable; no special preparation required.
- Acute illness, renal disease, or hypothyroidism may modestly elevate Lp(a).
- Estrogens (including oral contraceptives) and tamoxifen can lower Lp(a) levels.
- Lp(a) levels stable throughout life; single measurement typically sufficient.
Synonyms
- Lp(a).
- Lipoprotein little a.