Cardiovascular Disease (Non-traditional Risk Markers) - Risk Markers - CVD (Non-traditional)

Diagnosis

Indications for Testing

  • Known intermediate to high risk for CVD

Laboratory Testing

  • Newest ACC/AHA guidelines (2013) deemphasize use of any markers other than cholesterol (LDL, HDL) except on occasional individualized basis in intermediate- to high-risk patients
  • hs-CRP assay
    • Order in patients with intermediate 10-year risk (10-year predicted risk ≥5%) as assessed by Framingham risk score (see Framingham Cardiac Risk calculator); otherwise, this test is not recommended
    • Combine with Lp-PLA2 to increase accuracy of risk prediction
    • hs-CRP results used to assign risk  
      • <1.0 mg/L = low risk
      • 1.1-3.0 mg/L = average risk
      • 3.1-9.9 mg/L = high risk
      • ≥10 mg/L = very high risk
    • If initial value is >3.0 but <10 mg/L, repeat in 2 weeks
  • Lp-PLA2
    • Order in addition to hs-CRP in patients with intermediate to high 10-year risk (defined as borderline LDL-C 131 mg/dL or HDL-C 39 mg/dL) as assessed by Framingham risk score
  • Chronic kidney markers
    • No recommended testing if 10-year predicted risk as assessed by Framingham risk score is <5%
      • Estimated GFR and microalbumin testing in individuals with hypertension, diabetes mellitus (DM), CVD, and/or family history of CVD
      • Perform GFR and serum creatinine for all patients >65 years
  • APOE mutations
    • Consider for primary hypercholesterolemias/hyperlipidemias diagnosis
      • Most commonly type III hyperlipoproteinemia (HLP III)
    • Addition of APOE to existing risk models does not enhance predictive power of models; do not use routinely for assessment of cardiac risk
  • Apo A-1 and B
    • Addition of Apo A-1 and B to existing risk models does not enhance predictive power of models; do not use routinely for assessment of cardiac risk
      • May be used in addition to LDL-C monitoring as a non-HDL-C marker (LDL+IDL+VLDL) in patients with serum triglycerides ≥200 mg/dL
        • Apo B/Apo A-1 ratio may also be used as cholesterol/HDL-C ratio when used in scenario above
      • APOB mutation assessment is appropriate in inherited hypercholesterolemias
  • Homocysteine
    • Addition of homocysteine to existing risk models does not enhance predictive power of models; do not use routinely for assessment of cardiac risk
      • Homocysteine levels
        • ≤10 μmol/L – desirable
        • >10 μmol/L to <15 μmol/L – intermediate
        • ≥15 to 30 μmol/L – high
        • ≥30 μmol/L – very high
  • Lp(a)
    • Addition of Lp(a) to existing risk models does not enhance predictive power of models; do not use routinely for assessment of cardiac risk
    • Possible clinical uses (in patients with intermediate risk category)
      • Established atherosclerotic disease with normal lipid profiles
      • Recurrent arterial stenosis
      • Hyperlipidemia refractory to therapy
  • NT-proBNP/BNP
    • Addition of NT-proBNP/BNP to existing risk models does not enhance the predictive power of models; do not use routinely for assessment of cardiac risk

Screening

  • Most biomarkers are not recommended for routine use or for risk stratification of CVD and should not be ordered prior to determining Framingham risk score
    • May be useful in patients with intermediate 10-year risk using Framingham risk score of 10-20% for further risk stratification

Monitoring

  • Insufficient data to recommend use of most current non-traditional markers for monitoring therapy
  • Apo B can be used as an alternative to non-HDL-C levels in monitoring
    • Goal is 80 mg/dL for patients with CVD or diabetes mellitus and one risk factor; 90 mg/dL if no CVD but 2 risk factors

Clinical Background

Cardiovascular disease (CVD) is a major cause of morbidity and mortality in U.S. Novel biomarkers can be valuable additions to standard risk factors for CVD.

  • For further clinical background information regarding cardiovascular disease, refer to cardiovascular disease (traditional risk markers)
  • Biomarkers of cardiovascular disease

    Cardiovascular Biomarkers for the Detection of Cardiovascular Disease

    Atheroscleroses

    Traditional markers:

    • Total cholesterol
    • LDL-C/HDL-C
    • Total cholesterol/HDL-C ratio
    • Triglycerides

    Novel markers:

    • Lp(a)
    • Homocysteine
    • Apolipoproteins (Apo A, B, E)

    Inflammation

    Novel markers:

    • Acute phase reactants
      • hsCRP
      • SAA
    • Cytokines
      • IL-6, IL-8, IL-18
      • TNF-α receptors 1&2
    • Leukocytes (neutrophils)/platelets, endothelium
      • ICAM-1
      • VCAM-1
      • P-selectin, E-selectin
      • Lp-PLA2
      • MPO
      • CD40L
      • MCP-2
    • Coagulation/fibrinolysis

    Ischemia/Necrosis

    Traditional markers:

    • Troponins I & T
    • CK-MB

    Novel markers:

    • FABP
    • GP-BB
    • IMA
    • FFAu
    • WB-Chol
    • Sphingomyosin
    • MDA-LDL-C

    Myocardial Dysfunction

    Traditional markers:

    • NTproBNP/BNP

    Novel markers:

    • ST2

    BNP = b-type natriuretic peptide; CD40L = CD40 ligand; CK-MB = creatine kinase-muscle and brain; CRP = C-reactive protein; hs-CRP = high-sensitivity CRP; FABP = fatty acid binding protein; FFAu = unbound free fatty acid; GP-BB = glycogen phosphorylase - brain; IL = interleukin; HDL-C = high-density lipoprotein-cholesterol; ICAM = inter-cellular adhesion molecule; IMA = ischemia-modified albumin; LD = lactate dehydrogenase; LDL-C = low-density lipoprotein-cholesterol; Lp(a) = lipoprotein a; Lp-PLA2 = lipoprotein-associated phospholipase A2; MCP-2 = monocyte chemoattractant protein-2; MDA-LDL-C = malondialdehyde-modified LDL-C; MPO = myeloperoxidase; NTproBNP = N-terminal proBNP; PAPP-A = pregnancy-associated plasma protein A; PIGF = placental-derived growth factor; SAA = serum amyloid A; ST2 = soluble member of the interleukin-1 receptor family; TNF-α = tumor necrosis factor alpha; VCAM = vascular cell adhesion molecule; vWF = von Willebrand Factor; WB-Chol = whole blood choline

Recent Focus in Research for Novel Markers of CVD

  • hs-CRP

    hs-CRP

    CRP – most sensitive of the acute phase reactant proteins; elevated in the following

    • Acute insults
      • Elevates <2 hours in
      • Peaks and begins to decrease within 48 hours of acute insult if no other inflammatory event occurs
    • Arterial disease
      • hs-CRP is a marker of existing arterial disease and future risk
      • Healthy individuals with hs-CRP results in highest quartile (upper 25%) have 2-fold greater risk of developing atherosclerotic disease as compared with results in the lowest quartile
      • Basal CRP concentration remains stable over long periods of time
    Apolipoproteins

    Apolipoproteins

    Apo A-1

    • Primarily found in HDL-C where it activates lecithin acyltransferase, resulting in the removal of free cholesterol from extrahepatic tissues
    • Elevated Apo A-1 levels may protect against CVD and peripheral vascular disease
    • Reduced levels of Apo A-1 are one of the most reliable predictors of CVD

    Apo B

    • Main apolipoprotein of LDL-C and chylomicrons
    • Apo B makes cholesterol soluble for transport, leading to arterial deposition
    • Increased levels of LDL-C are associated with an increased risk of CVD
    • Autosomal dominant familial hypercholesterolemia type B is caused by mutations in the APOB gene
    • 40% of male and 20% of female APOB mutation heterozygotes develop CVD or hypercholesterolemia
    • Homozygotes or compound heterozygotes for two APOB mutations are at highest risk for hypercholesterolemia and CVD
    • Apo B is a surrogate marker for measuring non-LDL-C

    Apo E

    • Present on plasma lipoproteins, including chylomicrons, very low density lipoprotein (VLDL), and HDL-C
    • Serves as the ligand for lipoprotein receptors and plays an important role in lipoprotein metabolism
    • Given their differing receptor affinities, the Apo E isoforms alter plasma lipoprotein concentrations to varying degrees
    • APOE*3 allele is wild type and has no association with increased risk for CHD
    • APOE*E2 allele is associated with increased LDL-C and type III hyperlipoproteinemia  
    • APOE*E4 allele is associated with increased total and LDL-C and may contribute to CHD
    • Both E2 and E4 alleles are associated with increased plasma triglyceride concentrations
    Lp(a)

    Lp(a)

    • Heterogenous family of lipoprotein molecules consisting of an Apo A molecule attached to an Apo B-100 and a lipid-rich, LDL-like core
    • Concentrations that are generally very low are largely under genetic control
    • Elevated concentrations associated with increased risk of myocardial infarction, stroke, and CVD
    Homocysteine

    Homocysteine

    • Homocysteine is an amino acid that exists in the blood
    • Moderately elevated homocysteine is an independent predictor for atherosclerosis, CVD and thromboembolism
    • Risk of atherosclerosis increases progressively with increasing concentration of homocysteine
      • 10% of total risk may be attributable to elevated plasma homocysteine
      • Risk ratio of 1.18 for each 5 µmol/L homocysteine elevation (Humphrey 2008)
    • Methylenetetrahydrofolate reductase (MTHFR) is the enzyme involved in homocysteine metabolism
      • Enzyme inactivation causes an increase in plasma homocysteine
      • Most common genetic risk factors for hyperhomocysteinemia are MTHFR mutations C677T and A1298C
        • C677T homozygosity associated with 3-fold risk of early CVD
    • Very high concentrations are associated with homocystinuria, a rare inborn error of metabolism
      • Concentrations usually >50 μmol/L
      • Associated with ocular, skeletal, central nervous system, and vascular abnormalities
      • High risk for pulmonary embolism, stroke, and myocardial infarction
    Lp-PLA2

    Lp-PLA2

    • Calcium independent enzyme located primarily on the surface of circulating LDL-C 
      • Also known as platelet-activating factor acetylhydrolase
    • High levels associated with ischemic stroke; may be useful in risk assessment
    • Proatherogenic
      • Lp-PLA2 hydrolyzes LDL-C with resulting formation of lysophosphatidylcholine
      • Lysophosphatidylcholine is an attractant for macrophages, T-cells and vascular smooth muscle cells
    • Antiatherogenic
      • Functions to hydrolyze platelet activating factor
    • Arterial disease
      • Independent marker of moderate- and high-risk populations for CVD
      • Use in combination with hs-CRP to increase risk prediction
      • Has been found to be associated with ischemic stroke; may be useful in risk assessment
    ST2

    ST2

    • Member of the interleukin-1 receptor family
    • Secreted by myocytes under mechanical strain
    • Elevated concentrations of soluble ST2 occur in patients with heart failure and are strongly predictive of mortality
    Kidney disease markers – serum creatinine, cystatin, urine microalbumin

    Chronic Kidney Disease (CKD)

    Independent kidney disease markers for CVD risk

    • Serum creatinine – estimated glomerular filtration rate (GFR)
    • Urine microalbumin
    • Cystatin
      • May be a more powerful predictor than GFR, but needs more evaluation
  • Other, less-well-defined markers are also being researched, including IL-6, TNF-α, MPO and CD40L

Indications for Laboratory Testing

  • Tests generally appear in the order most useful for common clinical situations
  • Click on number for test-specific information in the ARUP Laboratory Test Directory
Test Name and Number Recommended Use Limitations Follow Up
C-Reactive Protein, High Sensitivity 0050182
Method: Quantitative Immunoturbidimetry

Recommend only if patient has intermediate 10-year risk of >5% using Framingham risk score 

Order in conjunction with Lp-PLA2 to enhance cardiovascular risk prediction

Should not be performed during acute illness

Significantly decreased CRP values may result in specimens from patients treated with carboxypenicillins

If first result is >3.0 mg/L but <10.0 mg/L, recommend repeating test at least 2 weeks later when patient is in metabolically stable state free of infection or acute illness

The lower of the two results should be used to determine patient’s risk

Apolipoprotein A-1 0050030
Method: Quantitative Nephelometry

Diagnose familial alpha-lipoprotein (Tangier disease)

May be used in addition to LDL-C monitoring as a non-HDL-C marker in patients with serum triglycerides ≥200 mg/dL

Do no use routinely for assessment of cardiac risk monitoring

   
Apolipoprotein B/A Ratio 0050028
Method: Quantitative Nephelometry

May be used in addition to LDL-C monitoring as a non-HDL-C marker in patients with serum triglycerides ≥200 mg/dL

May also be used as cholesterol/HDL-C ratio

Do not use routinely for assessment of cardiac risk

   
Apolipoprotein B 0050029
Method: Quantitative Nephelometry

Use to diagnose abetalipoproteinemia

Do not use routinely for assessment of cardiac risk

   
Apolipoprotein B (APOB) Mutation Detection 0055654
Method: Polymerase Chain Reaction/Fluorescence Monitoring

Confirm diagnosis of familial defective APOB-100 (FDB)

Identify a cause for inherited hypercholesterolemia

Screen individuals who are at risk for APOB mutation (positive family history of FDB)

Not recommended for asymptomatic patients <18 years

Mutations in other genes or other mutations in the APOB gene that may cause familial hypercholesterolemia or increased risk for CVD are not ruled out

Rare diagnostic errors may occur due to primer-site mutations

 
Apolipoprotein E (APOE) 2 Mutations, Cardiovascular Risk 0055566
Method: Polymerase Chain Reaction/Fluorescence Monitoring

Confirm a diagnosis of type III hyperlipoproteinemia (HLP III)

Identify a cause for HLP III or premature coronary heart disease (CHD)

Screen individuals with a family history of HLP III or premature CHD

Should not be ordered to assess Alzheimer disease risk

Mutations tested: E2, E3 (normal), and E4 alleles of the APOE gene

Clinical sensitivity – ~5% for individuals with CHD; 95% for individuals with HLP III  

Do not use routinely for assessment of cardiac risk

Genotyping preferred over phenotyping

Addition of APOE to existing risk models does not enhance predictive power of models for most patients

Not recommended in individuals <18 years

Rare Apo E isoforms and mutations in other genes that cause HLP III or an increased risk for CHD are not detected; if rare alleles are suspected, phenotyping by isoelectric focusing may be indicated

Rare diagnostic errors may occur due to primer-site mutations

 
Glomerular Filtration Rate, Estimated 0020725
Method: Quantitative Enzymatic

Recommend for individuals with hypertension, DM, CVD, or family history of CVD

   
Microalbumin, Urine 0050203
Method: Quantitative Immunoturbidimetry

Recommend for individuals with hypertension, DM, CVD, or family history of CVD

   
Creatinine, Serum or Plasma 0020025
Method: Quantitative Enzymatic

Recommend for individuals with hypertension, DM, CVD, or family history of CVD

   
Lipoprotein-Associated Phospholipase A2 (PLAC) 0081055
Method: Quantitative Enzyme-Linked Immunosorbent Assay

Order in conjunction with hsCRP in patients with intermediate to high 10-year risk to enhance CVD risk prediction

   
Lipoprotein (a) 0099174
Method: Quantitative Immunoturbidimetry

Most useful in patients with early CVD or family history of early CVD

Do not use routinely for assessment of cardiac risk

Addition to existing risk models does not enhance predictive power of models for most patients  
Homocysteine, Total 0099869
Method: Quantitative Enzymatic

Measure homocysteine levels for estimated risk level

Do not use routinely for assessment of cardiac risk

Addition to existing risk models does not enhance predictive power of models for most patients  
Additional Tests Available
 
Click the plus sign to expand the table of additional tests.
Test Name and NumberComments
VAP Cholesterol, Serum 0095263
Method: Ultra Centrifugation
LDL Subclasses 0050021
Method: Quantitative Electrophoresis
Methylenetetrahydrofolate Reductase (MTHFR) 2 Mutations 0055655
Method: Polymerase Chain Reaction/Fluorescence Monitoring

c.665C>T (previously c.677C>T), p.Ala222Val and c.1286A>C (previously c.1298A>C), and p.Glu429Ala mutations tested

C-Reactive Protein 0050180
Method: Quantitative Immunoturbidimetry

Should not be used for CVD risk assessment

LDL Cholesterol, Direct 0020257
Method: Quantitative Detergent Solubilization/ Enzymatic
HDL Cholesterol 0020053
Method: Detergent Solubilization/Enzymatic
Lipoprotein Electrophoresis 0080503
Method: Qualitative Electrophoresis/Quantitative Enzymatic/Detergent Solubilization
ST2, Soluble 2002270
Method: Quantitative Enzyme Immunoassay
LipoProfile by Nuclear Magnetic Resonance (NMR) 2002043
Method: Quantitative Nuclear Magnetic Resonance Spectroscopy
LipoProfile by Nuclear Magnetic Resonance (NMR), Particle Analysis Only 2003323
Method: Quantitative Nuclear Magnetic Resonance Spectroscopy
proBrain Natriuretic Peptide, NT 0050083
Method: Quantitative Electrochemiluminescent Immunoassay
Cystatin C, Serum 0095229
Method: Quantitative Nephelometry