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Beta-2-Glycoprotein I Antibody (IgG) with Reflex to B2GPI-Domain 1
Test Code12163
Includes
Beta-2-Glycoprotein I Antibody (IgG); Beta-2-Glycoprotein I-Domain 1 Antibody (IgG)
Preferred Specimen
3 mL Plasma.
Collection Instructions:
__Plasma (preferred):
__Centrifuge light blue-top tube 15 minutes at approximately
__1500 g within 60 minutes of collection. Using a plastic
__pipette, remove plasma, taking care to avoid the
__WBC/platelet buffy layer and place into a plastic vial.
__Centrifuge a second time and transfer platelet-poor plasma
__into a new plastic vial. Plasma must be free of platelets
__(<10,000/mcL).
__
__Serum:
__Allow blood to clot (10-15 minutes) at room temperature.
__Centrifuge to separate serum. Pour off serum and
__refrigerate as soon as possible.
Collection Instructions:
__Plasma (preferred):
__Centrifuge light blue-top tube 15 minutes at approximately
__1500 g within 60 minutes of collection. Using a plastic
__pipette, remove plasma, taking care to avoid the
__WBC/platelet buffy layer and place into a plastic vial.
__Centrifuge a second time and transfer platelet-poor plasma
__into a new plastic vial. Plasma must be free of platelets
__(<10,000/mcL).
__
__Serum:
__Allow blood to clot (10-15 minutes) at room temperature.
__Centrifuge to separate serum. Pour off serum and
__refrigerate as soon as possible.
Minimum Volume
1.5 mL Plasma
Other Acceptable Specimens
3 mL Serum
Transport Container
Plasma: 3.2% Sodium Citrate (lt. blue-top)
Serum
__Red-top (no gel)
__SST (red-top)
Serum
__Red-top (no gel)
__SST (red-top)
Transport Temperature
Plasma and Serum: Refrigerated preferred; Room temperature
_unacceptable; Frozen acceptable
_unacceptable; Frozen acceptable
Specimen Stability
Plasma or Serum
__Room temperature: 48 Hours
__Refrigerated: 14 Days
__Frozen: 30 Days
__Room temperature: 48 Hours
__Refrigerated: 14 Days
__Frozen: 30 Days
Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Yes • Yes
Methodology
Immunoassay
Setup Schedule
A.M. Sets up 6 days a week.
Report Available
Reports in 4 to 9 days.
Clinical Significance
The antiphospholipid syndrome (APS) is a systemic
autoimmune disorder characterized venous and/or arterial
thrombosis (intravascular blood clotting),
thrombocytopenia, recurrent fetal loss, and
moderate-to-high titers of antiphospholipid (aPL)
antibodies, lupus anticoagulant (LA), anti-cardiolipin
(aCL) antibodies and anti-Beta-2-glycoprotein I (aB2GPI)
antibodies.
aPL antibodies are autoantibodies that react with
negatively charged phospholipids (e.g. Cardiolipin). They
are frequently found in sera of patients with systemic
lupus erythematosus (SLE) and related diseases and are
typical for the development of secondary APS. The presence
of antiphospholipid antibodies in patients with no other
autoimmune diseases is characteristic of primary APS.
Because aCL antibodies are found in 80-90% of patients with
APS, this test is very sensitive for the diagnosis of the
syndrome. However, the aCL test is not specific to APS
because aCL antibodies can also be detected in other
autoimmune diseases, following administration of several
drugs, and in the aftermath of infectious diseases (e.g.,
syphilis, hepatitis C and infectious mononucleosis).
B2GPI, also known as apolipoprotein H, is a 54 kDa serum
cofactor (protein) that inhibits the intrinsic coagulation
pathway and is involved in the regulation of blood
coagulation. Detailed investigations about the nature of
the cardiolipin-B2GPI complex have shown that B2GPI is the
real autoantigen of anti-cardiolipin antibodies. In
addition to being a prerequisite for binding to
anti-cardiolipin antibodies, B2GPI has been identified as
the primary antigen for these antibodies. Hence, an assay
with a B2GPI bound solid phase will not bind antibodies
from other disease states, e.g., in syphilis positive
samples, and will show better overall disease specificity.
A definite diagnosis of APS requires the presence of at
least one clinical manifestation and one positive
laboratory test result. The clinical criteria include
thrombosis and one of the following three during pregnancy:
one or more pregnancy losses after the 10th gestational
week; one or more episodes of pre-term delivery before the
34th gestational week due to severe pre-eclampsia or severe
placental insufficiency; or three or more recurrent
pregnancy losses before the 10th gestational week. The
laboratory criteria include the detection of IgG aCL or
aB2GPI antibodies in moderate to high titers, in two
different measurements at least 12 weeks apart; or
detection of LA in two different measurements at least 12
weeks apart.
Anti-B2GPI antibodies have been reported to bind to
epitopes located primarily on domains 1, 4, and 5 of the
B2GPI molecule. Importantly, the main B2GPI epitope
specifically associated with antiphospholipid syndrome has
been reported to be a cryptic and conformation dependent
structure that involves different regions of domain 1. If
testing is positive for aB2GPI IgG antibodies, reflex
testing will be performed to determine if the antibodies
are directed to B2GPI domain 1. A positive B2GPI domain 1,
IgG antibody test result may be useful in identifying
patients at increased risk for arterial and venous
thrombosis and pregnancy morbidity.
autoimmune disorder characterized venous and/or arterial
thrombosis (intravascular blood clotting),
thrombocytopenia, recurrent fetal loss, and
moderate-to-high titers of antiphospholipid (aPL)
antibodies, lupus anticoagulant (LA), anti-cardiolipin
(aCL) antibodies and anti-Beta-2-glycoprotein I (aB2GPI)
antibodies.
aPL antibodies are autoantibodies that react with
negatively charged phospholipids (e.g. Cardiolipin). They
are frequently found in sera of patients with systemic
lupus erythematosus (SLE) and related diseases and are
typical for the development of secondary APS. The presence
of antiphospholipid antibodies in patients with no other
autoimmune diseases is characteristic of primary APS.
Because aCL antibodies are found in 80-90% of patients with
APS, this test is very sensitive for the diagnosis of the
syndrome. However, the aCL test is not specific to APS
because aCL antibodies can also be detected in other
autoimmune diseases, following administration of several
drugs, and in the aftermath of infectious diseases (e.g.,
syphilis, hepatitis C and infectious mononucleosis).
B2GPI, also known as apolipoprotein H, is a 54 kDa serum
cofactor (protein) that inhibits the intrinsic coagulation
pathway and is involved in the regulation of blood
coagulation. Detailed investigations about the nature of
the cardiolipin-B2GPI complex have shown that B2GPI is the
real autoantigen of anti-cardiolipin antibodies. In
addition to being a prerequisite for binding to
anti-cardiolipin antibodies, B2GPI has been identified as
the primary antigen for these antibodies. Hence, an assay
with a B2GPI bound solid phase will not bind antibodies
from other disease states, e.g., in syphilis positive
samples, and will show better overall disease specificity.
A definite diagnosis of APS requires the presence of at
least one clinical manifestation and one positive
laboratory test result. The clinical criteria include
thrombosis and one of the following three during pregnancy:
one or more pregnancy losses after the 10th gestational
week; one or more episodes of pre-term delivery before the
34th gestational week due to severe pre-eclampsia or severe
placental insufficiency; or three or more recurrent
pregnancy losses before the 10th gestational week. The
laboratory criteria include the detection of IgG aCL or
aB2GPI antibodies in moderate to high titers, in two
different measurements at least 12 weeks apart; or
detection of LA in two different measurements at least 12
weeks apart.
Anti-B2GPI antibodies have been reported to bind to
epitopes located primarily on domains 1, 4, and 5 of the
B2GPI molecule. Importantly, the main B2GPI epitope
specifically associated with antiphospholipid syndrome has
been reported to be a cryptic and conformation dependent
structure that involves different regions of domain 1. If
testing is positive for aB2GPI IgG antibodies, reflex
testing will be performed to determine if the antibodies
are directed to B2GPI domain 1. A positive B2GPI domain 1,
IgG antibody test result may be useful in identifying
patients at increased risk for arterial and venous
thrombosis and pregnancy morbidity.
