Description of Laboratory Test Results
Lipid Panel
Berkeley HeartLab recommendations for lipid tests results are in part
based on current guidelines of the National Cholesterol Education Program
(NCEP) (Third Report of the Expert Panel on Detection, Evaluation, and
Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III),
NIH Publication No. 01-3670, May 2001), but should be modified depending
on the presence or absence of other cardiovascular risk factors and history
of coronary artery disease.
LDL Segmented Gradient Gel Electrophoresis (LDL-S3GGE®) ‡
Seven regions (subclasses) are determined on LDL-S3GGE®.
The subclasses are defined as LDL I, IIa, IIb, IIIa, IIIb, and IVa, IVb. High
levels of subclasses LDL IIIa + LDL IIIb reflect an abundance of small LDL
particles and expression of the Atherogenic Lipoprotein Profile (ALP).
Reduction of LDL IIIa and LDL IIIb in CAD patients has been associated with
arteriographic benefit. Elevated levels of LDL subclass IVb reflect an
abundance of the smallest LDL subclass. LDL IVb > 10% is a negative indicator
and is associated with arteriographic progression. LDL-S3GGE®
is correlated to the gold standard for lipid subclassification – analytical
ultracentrifugation (ANUC). Å = Angstrom measurement.
HDL Segmented Gradient Gel Electrophoresis (HDL-S10GGE®) ‡
Five regions (subclasses) are determined on HDL-S10GGE®.
The subclasses are defined as HDL 2b, 2a, 3a, 3b, and 3c. HDL2b is the region
associated with reverse cholesterol transport efficiency. The average HDL2b in
an asymptomatic middle aged male and female population, who are LDL pattern A,
is approximately 18% and 26% respectively. The amount of HDL2b (determined by
Gradient Gel Electrophoresis) has been associated with coronary artery disease
severity, and progression over time (Johansson J, et al. Arteriosclerosis and
Thrombosis 1991;11:174-182). HDL-S10GGE® is
correlated to the gold standard for lipid subclassification – analytical
ultracentrifugation (ANUC). Å = Angstrom measurement.
Apoprotein E Genotype ‡
Apo E Genotypes are genetically fixed and present in combinations of E2, E3, and
E4. E 3/3 is the normal genotype. E 2/2, found in less than 1% of the
population, predisposes the patient to Type III Hyperlipidemia. E 4/4 and E 4/3
are associated with a predisposition to elevated cholesterol levels and risk of
CVD. Genotypes E 3/2, and E 4/2 are not consistently associated with lipid
abnormalities. Due to the unique nature of genetic testing, physicians may
suggest patients consider genetic counseling. Informed consent is recommended
and required for patients residing in the state of New York. Consent forms are
available from Berkeley HeartLab, Inc upon request.
Lipoprotein (a)
Lipoprotein (a) (Lp(a)) is an LDL particle with an abnormal protein attached.
High levels of Lipoprotein (a) are associated with an increased risk of developing
CAD.
Apoprotein A-I
Apolipoprotein A-I (Apo A-I) is a major apolipoprotein attached to HDL and
triglyceride-rich lipoproteins. Lower levels of Apo A-I have been reported in
patients with CAD.
Apoprotein B
Apolipoprotein B (Apo B) is the major apolipoprotein associated with LDL.
Higher levels of plasma Apo B may signify increased coronary disease risk even
when LDL-cholesterol is not in the high-risk range.
Apoprotein B-Ultra ‡
Apo B–Ultra is designed to remove interference from the ApoB-48 associated with
chylomicrons by ultracentrifugation, so an accurate ApoB-100 particle number is
reported.
Homocysteine
Homocysteine is a metabolic byproduct of methionine metabolism. Elevated levels
are associated with a 2-3 fold increased CVD risk. Values in excess of 14
µmol/ml are considered elevated (Graham et al. JAMA 1997;277:1775-1781.;
Malinow et al. Circulation 1993;87:1107-1114).
Fibrinogen (mass)
Fibrinogen is a plasma protein, which can be transformed by thrombin into a
fibrin clot. Values in excess of 277 mg/dl have been associated with a 2.4 fold
increase in coronary events compared to values less than 236 mg/dl (Heinrich et
al. Atheriosclerosis and Thrombosis 1994;14:54-59). Subjects with
elevated fibrinogen and elevated LDLC (> 163 mg/dl) have a 6.1 fold increase in
coronary risk. Each increase of 75 mg/dl of fibrinogen has been reported to
increase CAD mortality by 29% (Benderly et al. Arterioscler Thromb Vasc Biol.
1996;16:351-356). Berkeley HeartLab uses nephelometry to measure fibrinogen;
results cannot be used to assess coagulation status.
Insulin
Insulin is a protein involved with carbohydrate metabolism. It is elevated
postprandially in proportion to the carbohydrate content in a meal. Elevated
fasting insulin levels have been related to atherosclerosis risk particularly in
South Asian Men. The upper tertile is > 12.4 µU/ml (McKeigue PM et al.
Circulation 1993;87:152-161). The loss of estrogen at menopause is
associated with increased insulin levels. There is an overlap between insulin
levels in CAD and control patients.
C-Reactive Protein (high sensitivity)
C-Reactive Protein (CRP) is one of a number of “acute phase” proteins
and increases in response to some inflammatory stimuli. Elevated hs-CRP levels
have been associated with a significant increase in risk for cardiovascular
events (Ridker et al. NEJM 2000;342:836-843; Lagrand et al. Circulation
1999;100:96-102). Values >3.0 mg/L are considered high risk, between 1.0 mg/L
and 3.0 mg/L intermediate and <1.0 mg/L low risk, corresponding to approximately
two thirds and one third (tertiles) of adult population distributions. Due to
the wide individual variability, the recommended protocol for individual CRP
measurements suggests obtaining samples on three separate occasions (at least
one week apart). The mean value of the three is calculated as the
“average” value (DeMaat et al. Arterioscler,Thrombo Vasc Biol.
1996;16;1156-1162).
Lp-PLA2
Lp-PLA2 is associated with vascular inflammation specific to CVD. The
risk for Cardiovascular Disease events rises sharply when Lp-PLA2 exceeds 223
ng/ml. Values above 200 ng/ml are in the upper 25th percentile for a secondary
prevention Cardiovascular Disease-diagnosed American population. Elevated
Lp-PLA2 values are known to indicate an active atherogenic process
and are associated with prediction of CVD and stroke events.
NT-proBNP
N-terminal pro-Brain natriuretic peptide (NT-proBNP) is associated with
prediction of cardiac events when used as a biomarker of subclinical myocardial
stress or stretch (Blankenberg et al.HOPE study. Circ. 2006; 114;3:201-208;
McKie et al. Hypertension. 2006; 47:874-880) and is also used to aid CHF
diagnosis. When used as a prognostic biomarker, NT-proBNP levels above 125 pg/mL
suggest increased CVD risk in which further diagnostic studies may be considered
as clinically indicated. Levels above 450 pg/mL suggest structural or functional
cardiac dysfunction.
Q-LDL (IIIa+b) and Q-LDL (IVb)
Atherogenic subclass quantitation, Q-LDL(IIIa+b) and Q-LDL(IVb), provides a
measure of atherogenic LDL particles in mg/dL and are based upon results from
Apo B and LDL-S3GGE®.
‡ This test was developed and its performance
characteristics determined by BHL. It has not been cleared or approved by the
U.S. Food & Drug Administration (FDA). The FDA has determined that such
clearance or approval is not necessary. This test is used for clinical purposes.
It should not be regarded as investigational or for research. This laboratory
is certified under CLIA-88 as qualified to perform high complexity clinical
laboratory testing.
The “Clinical Abnormality Summary” statements listed on the
report form are based on single laboratory blood test results and do not
constitute the diagnosis of any diseases or any other illnesses or health
conditions for which the diagnosis can only be made by a qualified physician.
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