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Test Code CHEM147 Lipoprotein(a), Serum

Additional Codes

YLPA


Specimen Required


Supplies: Sarstedt Aliquot Tube, 5 mL (T914)

Collection Container/Tube:

Preferred: Serum gel

Acceptable: Red top

Submission Container/Tube: Plastic vial

Specimen Volume: 1 mL

Collection Instructions: Centrifuge and aliquot serum into plastic vial. Send refrigerated.


Useful For

Cardiovascular disease (CVD) risk refinement in patients with moderate or high risk based on conventional risk factors or patients with clinical suspicion of residual CV risk not identified by other lipid parameters

Method Name

Immunoturbidimetric Assay

Reporting Name

Lipoprotein(a), S

Specimen Type

Serum

Specimen Minimum Volume

0.5 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Serum Refrigerated (preferred) 7 days
  Frozen  30 days
  Ambient  24 hours

Reject Due To

Gross hemolysis Reject
Gross lipemia Reject
Gross icterus Reject
 

Clinical Information

Lipoprotein (a) [Lp(a)] consists of a low-density lipoprotein (LDL) particle that is covalently bound to an additional protein, apolipoprotein (a) [Apo(a)]. Apo(a) has high sequence homology with the coagulation factor plasminogen, and like LDL, Lp(a) contains apolipoprotein B100 (ApoB). Thus, Lp(a) is both proatherogenic and prothrombotic.

 

Lp(a) is an independent risk factor for coronary heart disease (CHD), ischemic stroke, and aortic valve stenosis. Lp(a) has been referred to as "the most atherogenic lipoprotein". The mechanism of increased risk is unclear but most likely involves progression of atherosclerotic stenosis via intimal deposition of cholesterol and promotion of thrombosis via homology to plasminogen.

 

Accurate immunochemical measurement of Lp(a) is complicated by the heterogeneity of Lp(a) molecular size. Due to the large number of polymorphisms (varying number of kringle domain repeats in the Apo[a] protein) in the population, any given individual can have an Apo(a) protein between 240 to 800 kDa. This heterogeneity leads to inaccuracies in all immunoassays. In addition, the degree of atherogenicity of the Lp(a) particle may depend on the molecular size of the Lp(a)-specific protein. However, the measurement of Lp(a) using immunoassays calibrated to molar units is recommended to minimize assay inaccuracies caused by Apo(a) isoform size.

 

Serum concentrations of Lp(a) are related to genetic factors, specifically the expression of Apo(a), and are largely unaffected by diet, exercise, and lipid-lowering pharmaceuticals. However, in a patient with additional modifiable CHD risk factors, more aggressive therapy to normalize these factors may be indicated if the Lp(a) value is also increased. In cases of extremely elevated Lp(a), lipoprotein apheresis may be considered.

Reference Values

≥18 years: <75 nmol/L

 

Reference values have not been established for patients who are less than 18 years of age.

Interpretation

Lipoprotein (a) [Lp(a)] concentrations of 75 nmol/L and above are linearly related to increased risk of cardiovascular events independent of conventional risk markers.

 

Values ≥75 nmol/L may suggest increased risk of coronary heart disease.

 

Values ≥125 nmol/L are considered a risk-enhancing factor for cardiovascular disease by several professional societies. Clinician-patient discussion of therapeutic strategy is warranted.

Cautions

Epidemiologic studies have shown lipoprotein (a) [Lp(a)] concentrations are lowest in non-Hispanic white, Chinese, and Japanese populations. The Hispanic population has a slightly higher median Lp(a) concentration, and, in the African American population, the median Lp(a) serum concentration is approximately 2 times higher than in the white population.

 

In very rare cases, gammopathy, type IgM (Waldenstrom macroglobulinemia) in particular, may cause unreliable results.

Method Description

This test is a particle enhanced immunoturbidimetric assay. Human lipoprotein (a) (Lp[a]) agglutinates with the latex particles coated with anti-Lp(a) antibodies.(Package insert: Tina-quant Lipoprotein(a) Gen.2 reagent. Roche Diagnostics; V2.0, 01/2015)

Day(s) Performed

Monday through Sunday

Report Available

1 to 3 days

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Test Classification

This test has been modified from the manufacturer's instructions. Its performance characteristics were determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information

83695

LOINC Code Information

Test ID Test Order Name Order LOINC Value
LIPA1 Lipoprotein(a), S 43583-4

 

Result ID Test Result Name Result LOINC Value
LIPA1 Lipoprotein(a), S 43583-4

Forms

If not ordering electronically, complete, print, and send 1 of the following forms with the specimen:

-Cardiovascular Test Request Form (T724)

-General Test Request (T239)