Antiplasmin [CO006600]
Related Information
Synonyms Alpha2-Antiplasmin; alpha2-Antiplasmin;
Plasmin Inhibitor
Abstract Antiplasmin is a major inhibitor of plasmin. Hereditary
antiplasmin deficiency is a rare familial bleeding disorder due
to excessive fibrinolysis.
Specimen Plasma
Container Blue top (sodium citrate) tube
Collection Routine venipuncture. If multiple tests are being
drawn, draw blue top tubes after any red top tubes but before any
lavender top (EDTA), green top (heparin), or gray top (oxalate/fluoride)
tubes. Immediately invert tube gently at least 4 times to mix. Tubes
must be appropriately filled. Deliver tubes immediately to the laboratory.
Storage Instructions Separate plasma from cells as soon as
possible; plasma may be stored on ice for up to 4 hours; otherwise
store frozen.
Causes for Rejection Specimen received more than 4 hours
after collection, tube not filled, clotted specimen
Turnaround Time Several days, because test is often sent
out
Special Instructions Specimens for functional assays should
not contain fibrinolysis inhibitors (eg, epsilon-aminocaproic acid,
aprotinin) or heparin. Elevated alpha2-macroglobulin
levels >200% may slightly interfere with functional assays.
Reference Interval Approximately 80% to 130% functional;
approximately 48-80 mg/dL antigen. Antiplasmin levels (measured
by antigen assay) are slightly lower during the first 5 days of
life.1
Use Not a commonly performed clinical assay. May be considered
in patients with strong evidence for a familial bleeding disorder
and normal test results for more common bleeding disorders, such
as von Willebrand disease.
Methodology
Functional (activity) assays: Excess plasmin is added to
patient plasma. Antiplasmin in the patient plasma binds to and inhibits
plasmin, forming a plasmin-antiplasmin complex. Residual plasmin
then cleaves a chromogenic substrate, releasing a colored compound
that can be detected spectrophotometrically. The amount of plasmin
detected is inversely proportional to the concentration of antiplasmin
in the patient specimen.
Antigen (immunologic) assay by radial immunodiffusion: Plasma
is placed in a cylindrical well of an agarose gel. The agarose gel
contains an antibody monospecific for antiplasmin. Antiplasmin in
the specimen diffuses from the well into the gel where it forms
a complex with the antibody, creating a precipitin ring. The size
of the ring is proportional to the amount of antiplasmin in the
plasma.
Additional Information Plasmin mediates fibrinolysis, and
antiplasmin inhibits plasmin. Activated factor XIII cross-links
antiplasmin to fibrin, and antiplasmin protects fibrin from plasmin-mediated
fibrinolysis. Antiplasmin also binds to plasminogen and may inhibit
plasminogen binding to fibrin. Antiplasmin is synthesized in the
liver. Acquired causes of decreased antiplasmin include liver disease,
thrombolytic therapy, and disseminated intravascular coagulation
(DIC). Hereditary deficiencies of antiplasmin are either type I
or type II. Type I deficiencies are quantitative, in which both
functional and antigen levels are reduced. Type II deficiencies
are qualitative, with decreased functional levels but normal or
near normal antigen levels.
Footnotes
1. Andrew M, Paes B, Milner R, et al, "Development of the Human
Coagulation System in the Full-Term Infant,"Blood, 1987,
70(1):165-72.
References
Lijnen HR, Okada K, Matsuo O, et al, "alpha2-Antiplasmin Gene Deficiency
in Mice Is Associated With Enhanced Fibrinolytic Potential Without
Overt Bleeding,"Blood, 1999, 93(7):2274-81.
Yoshinaga H, Hirosawa S, Chung DH, et al, "A Novel Point Mutation
of the Splicing Donor Site in the Intron 2 of the Plasmin Inhibitor
Gene,"Thromb Haemost, 2000, 84(2):307-11.
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