Under preventative services, Medicare Part B covers the basic lipid panel
(total cholesterol, high density lipoprotein-cholesterol (HDL-C),
triglycerides, and low-density lipoprotein-cholesterol (LDL-C) for
cardiovascular (CV) disease screening, every 5 years when ordered by a doctor.  
  
NCD 190.23 covers lipid panel testing for symptomatic patients for evaluating
atherosclerotic CV disease, to monitor the progress of patients on anti-lipid
dietary management, and pharmacologic therapy for various lipid disorders.  
  
This policy denies coverage for **all CV risk assessment panels,** except the
basic lipid panel, for symptomatic (with signs and symptoms) patients with
suspected or documented CV disease because panel testing is not specific to a
given patient's lipid abnormality or disease. The policy indicates the medical
indication(s) based on published scientific articles and consensus guidelines
for individual lipid biomarkers that may be covered to characterize a given
lipid abnormality or disease, to determine a treatment plan, or to assist with
intensification of therapy. Each individual lipid biomarkers must be
specifically ordered and the reason for the test order documented in the
patient's medical record. The policy denies coverage for all **non-lipid**
biomarkers when used for CV risk assessment including but not limited to,
biochemical, immunologic, hematologic, and genetic biomarkers for CV risk
assessment regardless of whether ordered in a panel or individually.  
  
The following biomarkers, when they are included in a CV risk assessment
panel, are non-covered:

  * Lipoprotein subclasses;
  * LDL particles;
  * Intermediate density lipoproteins;
  * High density lipoprotein AI9LpAI and AI/AII;
  * Lipoprotein(a);
  * Apolipoprotein B (Apo B), apo A-I and apo E;
  * Lipoprotein-associated phospholipase A2 (Lp-PLA2)
  * BNP
  * Cystatin C
  * Thrombogenic/hematologic actors
  * Interleukin-6 (IL-6), tissue necrosis factor- a (TNF- a) , plasminogen activator inhibitor-1 (PAI-1) and IL-6 promoter polymorphism
  * Free fatty acids
  * Visfatin, angiotensin-converting enzyme 1 (ACE2) and serum amyloid A
  * Microalbumin
  * Myeloperoxidase (MPO)
  * Homocysteine and methylenetetrahydrofolate reductase (MTHFR) mutation testing
  * Uric acid
  * Vitamin D
  * White blood cell count
  * Long-chain omega-3 fatty acids in red blood cell membranes
  * Gamma-glutamyltransferase (GGT)
  * Genomic profiling including CardiaRisk angiotensin gene
  * Leptin, ghrelin, adiponectin and adipokines including retinol binding protein 4 (RBP4) and resistin
  * Inflammatory markers including VCAM-1, P-selectin (PSEL) and E-selectin (ESEL)
  * Cardiovascular risk panels

Note #1: There is no Medicare benefit for screening CV risk assessment testing
for asymptomatic (without signs or symptoms of disease) patients. Screening
asymptomatic patients for cardiovascular risk is statutorily excluded by
Medicare and will not be addressed in this policy.  
  
Note #2: FDA approval/clearance means that a test/assay has analytical and
clinical validity. The FDA does not review clinical utility (that the
test/assay demonstrates improved patient outcomes). To meet Medicare's
"reasonable and necessary" criteria for coverage, a test/assay must have
proven clinical utility.  
  
 **Traditional vs Non-traditional CV Risk Assessment**  
During the last two decades, the interest in CV biomarkers as early screening
tools has risen dramatically, largely fueled by the recognition that
traditional CV risk factors (diabetes, smoking, hypertension and
hyperlipidemia) do not fully explain individual variation in CV risk, and by
advances in genetic and molecular research. Risk assessment for determining
the 10-year risk for developing CHD is traditionally carried out using the
Framingham risk score.  
  
Despite the Framingham risk-scoring tool, clinicians have sought non-
traditional lipid and other biomarker measurements to predict CV events. The
most promising biomarkers are the ones that closely correlate with the
pathophysiological process of the disease. In general, there is evidence that
some of these biomarkers may alter risk categorization (higher or lower)
compared to traditional risk prediction, but it has not been established that
changes in categorization provides clinically actionable information beyond
that of traditional lipid measures. In addition, no study has provided high-
quality evidence that measurement of non-traditional lipid and other
biomarkers leads to changes in management that improve health outcomes.  
  
To provide clinically useful knowledge, a biomarker should meet the following
criteria:

  * Adds clinical knowledge that improves patient outcomes (criteria for Medicare "reasonable and necessary");
  * Provides risk information that is independent of established predictors;
  * Is easy to measure and interpret in the clinical setting; and
  * Is accurate, reproducible, and standardized.

**High-sensitivity C-reactive protein (hs-CRP)**  
CRP is a protein produced in the liver during episodes of acute inflammation
or infection. The hs-CRP test measures CRP that is in the normal range for
healthy people and is used to distinguish people with low normal levels from
those with high normal levels. In recent years, prospective epidemiologic
studies have demonstrated that inflammation is essential for CV disease
pathogenesis and that high normal levels of hs-CRP correlate with an increased
risk of CV events such as myocardial infarction (MI), stroke, sudden cardiac
death, and peripheral vascular disease (PVD), even when lipid levels are
within acceptable ranges. The American Heart Association (AHA) and the US
Centers for Disease Control and Prevent (CDC) recommend averaging two hs-CRP
levels obtained two weeks apart. Based on hs-CRP test results, they recognize:
low (3.0 mg/L) risk groups.  
  
In 2009, the US Preventive Services Task Force (USPSTF) report on the use of
non-traditional risk factors noted there is insufficient evidence to recommend
the use of non-traditional risk factors to screen asymptomatic individuals
with no history of CHD to prevent CHD events. The non-traditional risk factors
in their recommendation included: hs-CRP, ankle-brachial index (ABI),
leukocyte count, fasting blood glucose level, periodontal disease, carotid
intima-media thickness, coronary artery calcification (CAC) score on electron
beam computerized tomography (EBCT), homocysteine level, and lipoprotein(a)
level. The USPSTF stated there is insufficient evidence to determine the
percentage of intermediate-risk individuals who would be reclassified by
screening with non-traditional risk factors, other than hs-CRP or ABI. For
individuals re-classified as high-risk by hs-CRP or ABI, data are not
available to determine whether they benefit from additional treatment. They
note the potential harms resulting from re-classification including the use of
medications without proven benefit and psychological effects. The USPSTF
stated that clinicians should continue to use the Framingham model to assess
CHD risk and guide risk-based preventive therapy.  
  
While data from the Physicians' Health Study and Framingham Heart Study have
shown that hs-CRP measurements may result in reclassification of an
individual's risk compared to standard risk prediction models, meta-analysis
including data from the second Northwick Park Heart Study (NPHS II) and the
Edinburgh Artery Study concluded that the ability of hs-CRP to reclassify risk
correctly was modest and inconsistent.  
  
The Jupiter trial, a randomized, double-blind, placebo-controlled trial of the
use of rosuvastatin vs placebo in the primary prevention of CVD in patients
without diabetes with LDL-C <130mg/dL and CRP =2 mg/dL, was associated with a
significant reduction in the primary endpoint of CV events. These findings
suggest that hs-CRP measurement in highly preselected patients may have
important clinical implications. However, the Jupiter study was not a trial of
hs-CRP because individuals with unknown or low hs-CRP concentrations were not
studied. Despite evidence that elevated hs-CRP levels are associated with
increased risk of CHD, it has not been determined whether hs-CRP is causally
related to CHD.  
  
In 2010, The American College of Cardiology Foundation and the American Heart
Association (ACCF/AHA) published guidance as to when and in whom to measure
blood levels of hs-CRP. The guidance states that hs-CRP levels may assist in
the selection of patients for statin therapy according to the following
criteria (Class IIa; Level of evidence (LOE): B):

  * Men >50 years of age, or women >60 years of age or older
  * LDL-C <130 mg/dL 
  * Patients not on lipid-lowering, hormone replacement, or immunosuppressant therapy
  * Patients without clinical CHD, diabetes, chronic kidney disease, severe inflammatory conditions, or contraindications to statins

For example, a patient may appear to have a low or low-moderate elevated risk
of CV events based on traditional risk factor scoring with cholesterol levels,
weight, level of exercise, smoking history, diabetes, and hypertension.
However, an elevated hs-CRP level would indicate that the cardiac risk may be
substantially greater than traditional risk factors suggest, and that
treatment might be considered. For patients who are already known to have high
risk, according to current recommendations, hs-CRP levels will not add any
substantially new information, since the patient should already be receiving
all available therapy including statins to reduce the risk.  
  
The ACCF/AHA recommended measurement of hs-CRP for CV risk assessment in
asymptomatic intermediate-risk men 50 years of age or younger, or women 60
years of age or younger (Class IIb; LOE B). Since screening (asymptomatic
patient) is statutorily excluded from coverage, hs-CRP testing for these
individuals is not a Medicare benefit. They found no benefit for hs-CRP
testing in asymptomatic high-risk adults or men and women below the ages
stated above. (Class III; LOE B).  
  
The Canadian Cardiovascular Society guidelines recommend hs-CRP testing in men
older than 50 and women older than 60 years of age who are at intermediate
risk (10-19%) according to their Framingham risk score and who do not
otherwise qualify for lipid-lowering therapy. They also state that subjects
who meet Jupiter criteria can be considered for treatment based on the results
of that study.  
  
In the National Academy of Clinical Biochemistry's (NACB) practice guidelines
on emerging CV risk factors, only hs-CRP met the stated criteria as a
biomarker for risk assessment in primary prevention. They recommended:

  * If the 10-year predicted risk, after standard global risk assessment, is <5%, hs-CRP should not be measured.
  * If the 10-year risk is 5-10%, it is expected that 10% might be reclassified to a higher risk group with the test.
  * If the risk is intermediate (10-20%), and uncertainty remains as to the use of preventive therapies such as statins or aspirin, then hs-CRP measurement might be useful for further stratification into a higher or lower risk category.

The NACB also recommended that:

  * Therapies based on hs-CRP should be based on a clinician's clinical judgment because benefits of such treatment are uncertain;There is insufficient data that therapeutic monitoring using hs-CRP
  * over time is useful to evaluate effects of treatment in primary prevention;
  * The utility of hs-CRP levels to motivate patients to improve lifestyle behaviors has not been demonstrated;
  * Evidence is inadequate to support concurrent measurement of other inflammatory markers in addition to hs-CRP for coronary risk assessment.

In 2012, the American Association of Clinical Endocrinologist gave a 2b
recommendation for the use of hs-CRP to stratify borderline CV risk in
patients with a standard risk assessment, or those with an LDL-C<130 mg/dL. A
European consensus guideline (2012) recommended that hs-CRP testing should not
be measured in asymptomatic low- and high-risk patients and gave a weak
recommendation to further stratify patient with an intermediate risk of CVD.

The AHA's statement on non-traditional risk factors and biomarkers in CV
disease in youth notes "There is currently no clinical role for measuring CRP
routinely in children when assessing or considering therapy for CVD risk
factors." The AHA also state that it is not clear whether high hs-CRP levels
during childhood and adolescence lead to an increased risk of CVD in adult
life. While lifestyle changes have been shown to decrease hs-CRP in children,
and statins reduce CRP in adults, the AHA indicates there is minimal
information available on the effect of statins on hs-CRP in children and
whether lowering hs-CRP in children mitigates preclinical disease or CVD in
adulthood. Similarly, the National Heart, Blood and Lung Institute (NHBLI)
guideline on CV risk in children and adolescents found insufficient evidence
to recommend hs-CRP testing in these patient groups.  
  
In summary, this contractor expects testing to be limited to the following
criteria:

  1. Patient has intermediate CV risk (10-20% risk of CVD per 10 years using the Framingham point score); **and**
  2. Patient has LDL-C between 100-130 mg/dL; **and**
  3. Patient has two or more CHD major risk factors, including 
    * Age (Men > 50 years; Women > 60 years)
    * Current cigarette smoking
    * Family history of premature CHD (CHD in male first degree relative <55; CHD in female fist degree relative <65 years of age)
    * Hypertension (Systolic > 140 mm Hg, or on anti-hypertensive medication)
    * Low HDL-C (<40 mg/dL)

The use of hs-CRP testing to evaluate the effects of treatment or to motivate
patients to improve lifestyle behaviors are not considered medically
reasonable and necessary, and therefore not covered by Medicare.  
  

**Lipoprotein subclasses**  
Lipoprotein subclass determination based on density, electric charge, and
other physical chemistry aspect of particles such as nuclear magnetic
resonance allow more specific characterization of the major subclasses (VLDL,
LDL, IDL and HDL). Studies showed that small, dense LDL particles were highly
associated with the occurrence of CVD and diabetes.  
  
**LDL Particles (LDL-P) (aka LDL or Lipoprotein Particles or Particle Number,
LDL or Lipid Subfractionation, Lipid Phenotyping, Nuclear Magnetic Resonance
or NMR Profile)**

Small dense LDL with elevated triglyceride levels and low HDL-cholesterol
levels constitute the "atherogenic lipoprotein phenotype" form of dyslipidemia
that is a feature of type II diabetes and the metabolic syndrome. Measurement
of LDL particle density has been proposed as a technique to further risk
stratification in patients with elevated LDL levels or for patients with
normal LDL levels who have other high-risk factors for CAD, or to predict
response to a particular therapy.  
  
Although great progress has been made in the development of refined
lipoprotein assessment and such measurements have helped in understanding the
atherosclerotic process, it is not known whether measurements beyond
traditional lipids can identify CV risk subgroups and how treatment would
differ based on subgroup classification. Furthermore, it is not known whether
this additional information helps the health care provider to identify with
greater precision and accuracy the person who will develop clinical or
subclinical CVD.  
  
The NACB does not recommend testing as there is insufficient data that
measurement of lipoprotein subclasses can identify CV risk subgroups, how
treatment would differ based on subgroup classification and whether, over
time, measurement is useful to evaluate the effects of treatments. In
addition, the 2010 ACCF/AHA guidelines for assessment of lipoprotein, other
lipoprotein parameters and modified lipids state that "measurement of lipid
parameters, including lipoproteins, apolipoproteins, particle size, and
density, beyond standard fasting lipid profile is not recommended for
cardiovascular disease risk assessment in asymptomatic adults."  
  
Unlike lipoprotein size or subclass measures, which seek to improve CV risk
assessment beyond conventional lipid testing, LDL particle number tests (NMR
LDL-P) and apoB are simply an alternate measure of LDL quantity. Current data
supports the ability of LDL particle number to provide clinically actionable
information beyond traditional lipid measures to adjudicate individual
response to treatment and guide adjustment in therapy. In addition, recent
data demonstrate that patients with established CHD, stroke, TIA, peripheral
arterial, or diabetes achieving NMR LDL-P < 1000 nmol/L during the course of
their normal medical care experienced a significant 22-25% reduction in risk
of CV events (myocardial infarction, revascularization, angina and stroke)
versus patients managed to LDL-C < 100 mg/dL at 12, 24, and 36 months follow-
up.  
  
LDL particle number (NMR LDL-P), rather than LDL size or subclass, has been
shown to be significantly associated with CV risk independent of traditional
lipid and established risk factors. The American Association of Clinical
Endocrinologists (AACE), the National Lipid Association (NLA), the American
Diabetes Association (ADA) in conjunction with the American College of
Cardiology (ACC), and the American Association of Clinical Chemistry (AACC)
have developed consensus position statement on lipoprotein particle management
in individuals at risk for CVD. Due to the prevalence of discordantly elevated
LDL-P despite achieving low LDL-C and non-HDL-C values, each endorses use of
LDL particle number to evaluate LDL response and aid decision making regarding
potential adjustment of therapy. The 2013 AACE Comprehensive Diabetes
Management Algorithm, as well as the 2015 joint AACE/American College of
Endocrinology Clinical Practice Guidelines for Comprehensive Diabetes Mellitus
Care, advocate specific LDL particle number goals for statin treated diabetic
patients at high CV risk.  
  
**Intermediate Density Lipoproteins (Remnant Proteins)**  
Intermediate density lipoproteins (IDLs) have a density that falls between
LDLs and VLDLs and may be referred to as remnant lipoproteins because they
vary in size and contain varying proportion of triglycerides and cholesterol.
Although there is abundant evidence the remnant lipoproteins are atherogenic,
and a risk factor for CAD, there is no evidence how testing improves patient
outcomes.  
  
 **High Density Lipoprotein (HDL) Subclass (Lipoprotein AI 9LpAI) and
Lipoprotein AI/AII (LpAI/AII) and/or HDL3 and HDL2**  
HDL cholesterol (HDL-C) is the risk indicator most often used in associated
with CHD risk. HDL subfractions have been used for risk prediction. However,
data is lacking how the subfractions aid in the diagnosis and management of
CHD. Neither the NCEP nor ACCF/AHA guidelines recommend the routine
measurement of HDL subspecies in CHD risk assessment.  
  
**Lipoprotein(a) (Lp(a))**  
Lp(a) is a modified form of LDL in which a large glycoprotein,
apolipoprotein(a) is bound to apolipoprotein B. It promotes foam cell
formation and the deposition of cholesterol in atherosclerotic plaques, and,
because it is structurally similar to plasminogen, Lp(a) may contribute to
clot formation. However, the complete role of lipoprotein(a) is not fully
understood.  
  
There is no standardized scale for measuring Lp(a) because there is no level
that is considered "normal". Because Lp(a) levels are controlled predominantly
by genes, cholesterol-lowering drugs have little effect on lowering Lp(a)
levels. Elevated Lp(a) is considered an independent risk factor for
cardiovascular events, including myocardial infarction, stroke, CVD, vein
graft restenosis, and retinal arterial occlusion, and may be used to identify
individuals who might benefit from more aggressive treatment of other risk
factors. However, regardless of the association between Lp(a) and CV disease,
there is no data to suggest that more aggressive risk factor modification
improves patient health outcomes.  
  
The NACB specifies that Lp(a) screening is not warranted for primary
prevention and assessment of cardiovascular risk. They comment that Lp(a)
measurement may be done at the physician's discretion if the risk is
intermediate (10%-20%) and uncertainty remains as to the use of preventive
therapies such as statins or aspirin (Recommendation - IIb; LOE - C). They
further note there is insufficient evidence to support therapeutic monitoring
of Lp(a) concentrations for evaluating the effects of treatment.  
  
Similarly, the 2010 ACCF/AHA guidelines conclude that apolipoproteins are not
recommended for CV disease risk assessment in asymptomatic adults. UpToDate
notes that Lp(a) is a modest, independent risk factor for CVD, especially MI,
but notes there are no clinical trials that have adequately tested the
hypothesis that Lp(a) reduction reduces the incidence of first or recurrent
CVD events.  
  
Lp(a) testing may be indicated in select patients, particularly intermediate
risk patient, to assist physicians with the use of preventive therapies.
Routine testing is not covered by Medicare.  
  
 **Apolipoprotein B (Apo B), Apolipoprotein A-I (Apo AI), and Apolipoprotein E
(Apo E)**  
Apo B is a constituent of LDL particles and serves as an indirect measurement
of the number of LDL particles. Consequently, elevated levels of Apo B suggest
increased levels of small dense LDL particles that are thought to be
atherogenic.

Apo AI is the major protein constituent of HDL-C. However, its measurement has
not been established as a clinically useful test in determining clinical
therapy for patients with CAD or dyslipidemia at the current time.

While Apo B and Apo A-I are thought to be the main structural proteins of
atherogenic and anti-atherogenic lipoproteins and particles, testing for these
compounds has not been validated as a tool for risk assessment. As such, the
2010 ACCF/AHA guidelines indicate that apolipoproteins testing is not
recommended for CV risk assessment in asymptomatic adults. However, AACE
recommends Apo B testing to assess residual risk in patients for CAD (even
when LDL-C levels are controlled) in patient when the triglyceride
concentration is >150 mg/dL or the HDL-C concentration is <40 mg/dL. Medicare
expects testing to be limited to assessment of residual risk in patients with
CAD with triglyceride concentrations of >150 mg/dL or HDL-C of <40 mg/dL.

Apo E, the major constituent of VLDL and chylomicrons, acts as the primary
binding protein for LDL receptors in the liver and is thought to play a role
in lipid metabolism. Although some individuals hypothesize that Apo E
genotypes may be useful in the selection of drug therapy, the value of Apo E
testing in the diagnosis and management of CHD is insufficient and needs
further evaluation.  
  
The National Cholesterol Education Program (NCEP) expert panel concluded that
Apo AI is carried in HDL, and it is usually low when HDL is reduced. A low Apo
AI thus is associated with increased risk of CHD, but not independently of low
HDL. Whether it has independent predictive power beyond HDL-C is uncertain and
its measurement is not recommended for routine risk assessment in Adult
Treatment Panel (ATP III) Guidelines.  
  
**Testing for Lipoproteins**  
  
**Apolipoproteins**  
Apolipoproteins are measured in routine clinical laboratories with the use of
immunonephelometric or immunoturbidimetric assays. ApoB reflects the number of
potentially atherogenic lipoprotein particles because each particle of VLDL,
IDL, LDL, and lipoprotein(a) particle carries on its surface 1 Apo B100
protein. Most of plasma Apo B is found in LDL particles. HDL particles do not
carry Apo B. Instead, they carry Apo AI, which does not correspond directly to
the concentration of HDL particles in a 1-to-1 fashion.  
  
**LDL Gradient Gel Electrophoresis (GGE) (used by Berkeley Heart Lab,
Berkeley, CA)**  
GGE is the most commonly used lab technique to measure LDL particle density.
It has been promoted as an important criteria of CHD risk, and as a guide to
drug and diet therapy in patients with CAD. While the measurement of LDL
subclass patterns may be useful in elucidating possible atherogenic
dyslipidemia in patients without abnormal total cholesterol, HDL, LDL, and
triglycerides, there is inadequate evidence that LDL sub-classification by GGE
improves outcomes in patients with CV disease.  
  
**Density Gradient Ultracentrifugation (DGU) (used by Atherotec Inc,
Birmingham, AL)**  
The Vertical Auto Profile (VAP) test measures the relative distribution of
cholesterol within various lipoprotein subfractions, quantifying the
cholesterol content in the VLDL, IDL, LDL, lipoprotein(a), and HDL subclasses.
It includes components (e.g., total cholesterol, direct measured LDL-C, HDL-C,
and triglycerides), LDL density (i.e. pattern A versus pattern B), IDL, HDL
sub types, VLDL density and Lp(a), and non-lipid CV risk assessment biomarkers
including hs-CRP, homocysteine, Lp-PLA2, Apo-E genotype, vitamin D, cystatin,
and NT-proBNP.  
  
**Nuclear Magnetic Resonance Spectroscopy**  
In this method (NMR LipoProfile is FDA cleared and available from LipoScience
Inc, Raleigh, NC) particle concentrations of lipoprotein subfractions of
different size are obtained from the measured amplitudes of their lipid methyl
group NMR signals. Lipoprotein particle sizes are then derived from the sum of
the diameter of each subclass multiplied by its relative mass percentage based
on the amplitude of its methyl NMR signal.  
  
Note: FDA clearance does not mean the test has clinical utility.  
  
 **Ion-Mobility Analysis**  
This method (available from Quest Diagnostics Inc., Madison, NJ) measures both
the size and concentration of lipoprotein particle subclasses on the basis of
gas-phase differential electric mobility.  
  
**Summary of Lipoprotein Testing**  
At the current time, none of the above tests for lipoproteins have better
predictive strength than total/HDL-C ratio and there has been no clear benefit
for measuring particle number in most studies to date. Additional research is
needed to establish the utility of following changes in lipoproteins as a
therapeutic target and determine if any subgroups of patients benefit.  
  
**Lipoprotein-Associated Phospholipase A2 (Lp-PLA2)**  
Lp-PLA2 is also known as platelet activating factor acetylhydrolase. This
enzyme hydrolyzes phospholipids and is primarily associated with LDLs. It has
been suggested that this enzyme has a proinflammatory role in the development
of atherosclerosis. Studies show that Lp-PLA2 is an independent predictor of
CV risk but fail to demonstrate improved health outcomes. To improve outcomes,
studies must demonstrate how risk factors improve risk classification and
change in physician practice to improve patient outcomes.  
  
The NCEP ATP III panel concluded that routine measurement of inflammatory
markers (including Lp-PLA2) for the purpose of modifying LDL-cholesterol goals
in primary prevention is not warranted. In the 2010 ACCF/AHA guidelines for
assessment of CV risk, the experts concluded "lipoprotein-associated
phospholipase (Lp-PLA2) might be reasonable for cardiovascular risk assessment
in intermediate risk asymptomatic adults". However, at the current time, it is
not known whether Lp-PLA2 concentrations are clinically effective for
motivating patients, guiding treatment, or improving outcomes.  
  
**B-type Natriuretic Peptide (BNP)**  
BNP and NT-proBNP, hormones produced by cardiocytes in response to hemodynamic
stress, have emerged as preferred biomarkers for assessing heart-related
stress. There is evidence that these hormones provide prognostic information
of mortality and first CV events beyond traditional risk factors. However,
there is currently no evidence that treatment or intervention based on the
increased risk implied by these biomarkers improves patient outcomes.  
  
These hormones do play a role in the acute setting for use in diagnosing
decompensated heart failure.  
  
**Cystatin C**  
Cystatin C, encoded by the CST3 gene, is a small serine protease inhibitor
protein secreted by all functional cells in the body. It is used as a
biomarker for renal function and in CV risk assessment, although there is no
evidence that this marker improves outcomes when used in clinical care. The
NACB guidelines on Biomarkers of Renal Function and Cardiovascular Disease
Risk do not recommend testing. The NCEP advocates clinical studies to
characterize the utility of these markers in the global assessment of CV
disease risk.  
  
**Thrombogenic/Hematologic Factors**  
Hematologic factors including coagulation factors and platelets play a role in
acute coronary syndrome, although the precise mechanism is not known. That
platelets are involved in this process is supported by strong evidence that
aspirin and other antiplatelet therapies reduce the risk of myocardial
infarction.  
  
Fibrinogen has also been associated with CHD risk. A high fibrinogen level is
associated with increased risk for coronary events, independent of cholesterol
levels, while a low fibrinogen indicates a reduced risk even with high
cholesterol levels. Other hemostatic factors associated with increased
coronary risk include, but are not limited to, activated factor VII (aFVII),
tissue plasminogen activator (tPA), plasminogen activator inhibitor-1 (PAI-1),
von Willebrand factor (vWF), Factor V Leiden (FVL), Factor II (F2), Protein C
(PC), and antithrombin III.  
  
In 2009, the NACB guidelines reported there was sufficient data that
fibrinogen is an independent marker of CVD risk. In addition, measurement of
fibrinogen was not recommended because they expressed analytical concerns
regarding insufficient assay standardization and uncertainty in identifying
treatment strategies. Additionally, the NCEP expert panel concluded "ATPIII
does not recommend measurement of prothrombotic factors as part of routine
assessment of CHD risk". They indicated that the strength of the association
between thrombogenic/hemotologic factors and CHD risk has not been defined and
recommended clinical trials that target specific prothrombotic factors.  
  
D-dimer is associated with an increased risk of venous and arterial thrombotic
events, irrespective of baseline vascular disease, even after adjusting for
confounders such as age, smoking, and diabetes. In CVD, an increased fibrin
turnover represents not only a prothrombotic state, but also is a marker for
the severity of atherosclerosis. Although D-dimer is a simple test that is
widely available, it remains unclear whether D-dimer plays a causal role in
the pathophysiology of CV adverse events, or whether D-dimer is simply a
marker of the extent of disease.  
  
 **Interleukin-6 (IL-6), Tissue Necrosis Factor- a (TNF-a), Plasminogen
Activator Inhibitor-1 (PAI-1), and IL-6 Promoter Polymorphism**  
Adipose tissue is a prominent source of PAI-1. Recent data indicates there is
continuous production of large amounts of active PAI-1 in platelets that may
contribute to clot stabilization. PAI-1 is the primary physiological inhibitor
of plasminogen activation. Increased PAI-1 expression acts as a CV risk factor
and plasma levels of PAI-1 strongly correlate with body mass index (BMI).
Similar associations have been reported between PAI-1 activity and plasma
insulin and triglyceride levels in patients with CAD and diabetes. However,
there is no data that PAI-1 testing changes physician management to improve
patient outcomes.  
  
IL-6, an inflammatory cytokine, is involved in metabolic regulation of CRP.
IL-6 plays an important role in the process of rupture or erosion of
atherosclerotic plaques, and its serum levels are elevated during these
events. At the current time, there is no consensus on IL-6 assay methods or
reference values, and no data that demonstrates IL-6 testing changes physician
management to improve patient outcomes.  
  
Early in atherosclerotic plaque formation, leukocytes adhere to and are
entrapped in the endothelial wall, a process mediated by inflammatory adhesion
molecules such as P-selectin and ICAM-1 that are modulated by TNF-a. However,
to date, these biomarkers have not provided additional predictive power above
that of traditional lipid markers.  
  
Because a polymorphism in the promoter region of IL-6 (174 bp upstream from
the start site) appears to influence the transcription of the IL-6 gene and
plasma levels of IL-6, this functional polymorphism was considered a candidate
gene in the development of CV disease. However, multiple studies have produced
inconsistent findings. In a large population-based study, no significant
relationship between IL-6 promoter polymorphism and risk of CHD was
identified. The authors concluded that IL-6-174 promoter polymorphism is not a
suitable genetic marker for increased risk of CHD in person aged 55 years or
older.  
  
 **Free Fatty Acids (FFA, Saturated and Unsaturated)**  
The role of plasma FFA in thrombogenesis in humans is poorly established and
no strong direct evidence is available. Increasing plasma FFA concentration is
known to induce endothelial activation, increase plasma MPO level, and promote
a prothrombotic state in non-diabetic healthy subjects. Studies are ongoing to
demonstrate the role of FFA in the pathogenesis of atherosclerosis. However,
at the current time, there is sparse data on its role in early atherosclerosis
and no evidence how testing improves patient outcomes.  
  
 **Visfatin, Angiotensin-Converting Enzyme 2 (ACE2) and Serum Amyloid A**  
Visfatin is an active player promoting vascular inflammation and associated
with atherosclerosis-related disease. It is involved in cytokine and chemokine
secretion, macrophage survival, leukocyte recruitment by endothelial cells,
vascular smooth muscle inflammation, and plaque destabilization. Although
visfatin has emerged as a promising pharmacological target in the context of
CV complications, there is no evidence how testing improves patient outcomes.  
  
The renin-angiotensin system (RAS) plays a major role in the pathophysiology
of CVD. The enzyme angiotensin-converting enzyme (ACE) converts angiotensin I
into the vasoconstrictor, angiotensin II, the main effector of the renin-
angiotension system. It has been suggested that circulating ACE2 may be a
marker of CVD with low levels of ACE2 in healthy individuals and increased
levels in those with CV risk factors or disease. However, larger clinical
studies are needed to clarify the role of ACE2 as a biomarker of CVD,
determine the prognostic significance of circulating ACE2 activity, and assess
whether the measurement of ACE2 will improve CVD risk prediction.  
  
Serum amyloid A (SAA) is a sensitive marker of inflammation, and its elevation
has been implicated in obesity and in CVD. It is a highly conserved acute-
phase protein, stimulated by proinflammatory cytokines such as IL-6, TNF,
interferon-gamma, and transforming growth factor-beta (TGF-B). SAA is also a
kind of apolipoprotein that is involved in cholesterol metabolism. However,
there is sparse data on its role in early atherosclerosis and no evidence how
testing improves patient outcomes.  
  
 **Microalbumin**  
Microalbuminuria is both a renal risk factor and a CV risk factor in patients
with diabetes, and particularly a risk marker of CV mortality in the general
population. Microalbuminuria also appears to be a sensitive marker for
detecting new onset of hypertension and diabetes. However, for albuminuria to
be a target for therapy, one needs to prove that lowering of albuminuria per
se is cardioprotective. Albuminuria-lowering effect of antihypertensive
agents, particularly those that interfere with RAS, and the use of statins and
glucoseaminoglycans have been proved in randomized, controlled trial to be
cardioprotective. However, few have been directed at albuminuria lowering per
se to evaluate the effect on CV outcome. The question remains as to whether
microalbuminuria is the consequence or the cause of organ damage, particularly
whether high levels of albuminuria in young children reflect normal
physiological variations in endothelial function associated with CV and renal
risk in later age. While albumin excretion levels may represent a primary
marker for success of intervention strategies aimed at repairing vascular
function, there is no data how testing improves patient outcomes at the
current time.  
  
**Myeloperoxidase (MPO)**  
Elevated levels of myeloperoxidase, secreted during acute inflammation, are
thought by some to be associated with coronary disease and predictive of acute
coronary syndrome in patients with chest pain. Many studies have implicated
MPO in the pathogenesis of atherosclerosis, showing that it is enriched within
atheromatous plaques. Inflammatory cells recruited into the vascular wall
release MPO-derived reactive oxygen species that can promote endothelial
dysfunction by reducing the bioavailability of nitric oxide, generate
atherogenic oxidized-LDL, and modify HDL, impairing its function in
cholesterol efflux. However, at the current time there is insufficient data to
demonstrate that plasma MPO can predict CHD independent of other CVD risk
factors and there is no data that demonstrates how plasma MPO levels affect
management of individuals at risk for or patients with CHD.  
  
PPAR- _y_ is a key regulator of fatty acid metabolism, promoting its storage
in adipose tissue and reducing circulating levels of free fatty acids.
Activation of PPAR- _y_ has favorable effects on surrogate measures of
adipocyte function, insulin sensitivity, lipoprotein metabolism, and vascular
structure and function. However clinical trials of thiazolidinedione PPAR- _y_
activators have not provided conclusive evidence that they reduce CV morbidity
and mortality.  
  
At the current time, there is no clinical data that demonstrates the clinical
utility of testing for lipid peroxidation, isoprostanes, malondialdehyde,
nitrotyrosine, S-glutathionylation, oxidized LDL, or oxidized phospholipids.
Additionally, genetic testing for genes that regulate cellular and systemic
oxidative stress, including but not limited to, nuclear factor-2 (Nrf-2),
peroxisome proliferator-activated receptor gamma-co-activator 1alpha (PCG-1a),
and the thioredoxin family or proteins have no clinical data that demonstrates
utility.  
  
**Homocysteine and Methylenetetrahydrofolate Reductase (MTHFR) Mutation
Testing**  
Homocysteine is an amino acid found in the blood. Observational evidence
generally supports the association of homocysteine levels with CV risk,
particularly observational data that patients with hereditary homocystinuria,
an inborn error of metabolism associated with high plasma levels of
homocysteine, have markedly increased risk of CV disease. Folic acid and the B
vitamins are involved in the metabolism of homocysteine. Several studies found
the higher levels of B vitamins are associated with lower homocysteine levels,
while other evidence shows that low levels of folic acid are linked to a
higher risk of CHD and stroke. However, large randomized controlled trials do
not support a protective effect of folic acid supplementation (rectifying
homocysteine levels) in cardiovascular disease.  
  
MTHFR is a key enzyme in folate metabolism. Two variants of the MTHFR
polymorphisms result in reduced enzyme activity, impaired methylation and
increased risk of CVD, stroke, and hypertension. MTHFR mutation testing has
been advocated to evaluate the cause of elevated homocysteine levels.  
  
However, in 2009, the US Preventive Services Task Force (USPSTF) concluded
that the evidence was insufficient to assess the benefits and harms of using
non-traditional risk factors to screen asymptomatic adults with no history of
CHD to prevent CHD events. Homocysteine was one of the non-traditional factors
considered in the recommendation. In 2010, later updated in March 2014, the
AHA stated that a causal link between homocysteine levels and atherosclerosis
has not been established and noted that high homocysteine levels is not a
major risk factor for CV disease. The 2012 American Association of Clinical
Endocrinologists (AACE) guidelines for management of dyslipidemia and
prevention of atherosclerosis stated that testing for homocysteine, uric acid,
PAI-1, or other inflammatory markers is not recommended.  
  
 **Uric acid**  
A recent systemic review and meta-analysis suggests that elevated uric acid
levels may modestly increase the risk of stroke and mortality. However, future
studies are needed to determine whether lowering uric acid levels has any
beneficial effects on stroke risk. Data is inadequate to show that uric acid
testing changes physician management to improve patient outcomes.  
  
**Vitamin D**  
Low levels of vitamin D are an independent risk factor for CV death in
populations without pre-existing CV disease. However, systematic reviews on
interventional vitamin D supplementation and CV disease risk reported that
vitamin D supplementation had no effect on cardiovascular disease risk,
indicating a lack of a causal relationship.  
  
An additional concern regarding vitamin D testing is the considerable
variation between results obtained with the various methods (competitive
immunoassays, direct detection by high performance liquid chromatography or
liquid chromatography combined with tandem mass spectrometry), as well as
between laboratories. Immunoassay technologies are less sensitive and specific
for vitamin D than liquid chromatography with or without mass spectrometry.  
  
 **WBC**  
A large body of data from prospective studies has established an association
of leukocyte count with increased risk for CVD events. Leukocytes are thought
to play a role in the development and/or progression of atherosclerotic
plaques and their rupture due to their proteolytic capacity and oxidative
properties. WBC count is correlated with other coronary disease risk factors,
including cigarette smoking, BMI, cholesterol level, HDL-C (inversely),
triglycerides, diabetes and blood glucose level, physical activity
(inversely), and blood pressure. However, the NACB does not recommend WBC
testing because clinical utility in reclassifying risk level and identifying
treatment strategies is not known.  
  
 **Long-chain Omega-3 Fatty Acids in Red Blood Cell (RBC) Membranes**  
It has been proposed that the fatty acid composition of RBCs are an index of
long-term intake of eicosapentaenoic (EPA) plus docosahexaenoic (DPA) acids.
The omega-3 fatty acids are considered a new modifiable and clinically
relevant risk factor for death from CHD. Most studies to date have focused on
the association between fish consumption and risk of CHD. In the Rotterdam
Study, analysis of EPA plus DHA and fish intake was assessed in relation of
incident heart failure (HF). With nearly 5300 study individuals, the authors
concluded that their findings did not support a major role for fish intake in
the prevention of HF. Not only is there no association between fish intake and
EPA+DHA levels regarding prevention of HF, there is no scientific evidence
regarding how measurements of RBC omega-3 fatty acids composition would affect
management of individuals at risk for or patients with CHD. A recent article
(Marai, 2014) notes that the available data do not support testing for omega-3
polyunsaturated fatty acids (EPA + DHA) among healthy subjects and patients
with specific cardiac diseases.  
  
**Gamma-glutamyltransferase (GGT)**  
GGT, a marker of excessive alcohol consumption or liver disturbance, is an
enzyme catalyzing the first step in extracellular degradation of the anti-
oxidant glutathione and is thought to play a role in the atherosclerotic
process. Coverage for GGT is limited to the indications and limitations
specified in CMS NCD 190.32. Whether serum levels of GGT can aid in the
detection of individuals at high risk for incident CV events is under
investigation. Despite its potential role in stratifying patient risk, there
is no evidence testing improves patient outcomes.  
  
**Gene Mutations (any methodology) and Genomic Profiling**  
Proponents of molecular CV profile testing argue that improvement in CVD risk
classification leading to management changes that improve outcomes warrants
coverage of these tests. However, the Evaluation of Genomic Applications in
Practice and Prevention Working Group (EWG) found insufficient evidence to
recommend testing for 9p21 genetic variant or 57 other variants in 28 genes to
assess risk for CVD in the general population, specifically heart disease and
stroke.  
  
The following genes were included in the EWG's assessment: ACE, AGT, AGTR1,
APOB, APOC3, APOE, CBS, CETP, CYBA, CYP11B2, F2, F5, GNB3, GPX1, IL1B, LPL,
ITGB3, MTHFR, MTR, MTRR, NOS3, PAI-1, PON1, SELE, SOD2, SOD3, TNF, and 9p21.
The EWG found that the magnitude of net health benefit from the use of any of
these tests alone or in combination is negligible.  
  
CardiaRiskTM (Myriad, Salt Lake UT) markets a genetic test to identify a
mutation in the AGT genes. This test supposedly identifies specific
hypertensive patients at increased risk of CV disease and identifies patients
likely to respond to antihypertensive drug therapy. However, at the present
time there is no literature that points to clinical utility for this test.  
  
**Leptin, Ghrelin, Adiponectin, and Adipokines including Retinol Binding
Protein 4 (RBP4) and Resistin**  
Leptin, a satiety factor secreted by adipocytes that is instrumental in
appetite regulation and metabolism, is elevated in heart disease. In a recent
study, leptin levels and proinflammatory high-density lipoprotein (piHDL) when
combined into a risk score (PREDICTS) confers 28-fold increased odds of the
presence of any current, progressive, or acquired carotid plaque and
significantly associated with higher rates of intima-media thickness. However,
there is no data that demonstrates how measurement of leptin levels affects
management of individuals at risk for or patients with CHD.  
  
Ghrelin is a hormone produced in the stomach and pancreas that plays a role in
hunger and weight gain. In a recent study, ghrelin when incorporated in the CV
risk model improved the prediction of CVD events in hypertensive patients with
reclassification of roughly 21%. However, there is no evidence how testing
improves patient outcomes.  
  
Adiponectin is an adipose-specific hormone that has anti-inflammatory
properties and is protective against obesity. Particularly in children,
measurement of total adiponectin or high-molecular-weight adiponection (HMW
adiponectin) as a biomarker for insulin sensitivity and/or as a risk factor
for CVD is gaining support. However, the additive value of adiponectin levels
remains unclear and how it changes patient outcomes is not known. It is not
recommended clinically in children or adults.  
  
RBP4 is gaining recognition as an adipokine that may play an important role in
obesity and insulin resistance. The relationship between RBP4 and other
traditional and non-traditional risk factors for CVD, such as inflammatory
factors and/or oxidative stress, have not been confirmed in larger
populations, and causality has not been established.  
  
Resistin is an adipokine expressed highly in visceral compared with
subcutaneous adipose tissue. In the Study of Inherited Risk of Coronary
Atherosclerosis (Reilly, 2003), resistin levels were positively correlated
with higher coronary calcium scores and correlated with higher levels of
soluble TNF-a, receptor-2, Lp(a), and IL-6. The resistin gene (RETN)
polymorphism (bp -420 and +299) leads to increased concentrations of the
resistin peptide in circulation, which is associated with cardiomyopathy and
CAD. One study suggests that in addition to primary risk factors (total
cholesterol, LDL, triglycerides, and low concentrations of HDL), resistin
cytokine may be a risk factor for CVD. However, there is no clinical role for
measuring resistin as no data demonstrates how measurement of resistin levels
affects management of individuals at risk for or patients with CHD.  
  
 **Inflammatory Markers - VCAM-1, ICAM-1, P-selectin (PSEL) and E-selectin
(ESEL)**  
Clinical studies have shown that elevated serum concentrations of cell
adhesion molecules such as inter-cellular adhesion molecule-1 (ICAM-1),
vascular adhesion molecule-1 (VCAM-1), E-selectin (ESEL), and P-selectin
(PSEL) may contribute to CVD through their inflammatory effects on the
vascular endothelium and be independent risk factors for atherosclerosis and
cardiovascular disease (CVD). However, at the current time, testing for these
inflammatory markers has not been confirmed in larger populations, causality
has not been established, and testing has not resulted in improved patient
outcomes.