Laboratory Studies
Appropriate testing methodology (ie, functional vs antigenic, biologic vs chromogenic substrate assays) is an important consideration in the workup of patients with alpha2–plasmin inhibitor (alpha 2-PI) deficiency.
Testing blood during acute bleeding events may show reduced levels of factors, which may rise to reference range levels when patients are stable. Therefore, testing patients repeatedly when they are in a stable state is important to confirm the diagnosis.
The functional and antigenic levels of alpha2-PI are reduced to a similar extent in most patients with severe alpha2-PI deficiency. Patients with a dysfunctional molecule who have reduced functional activity with reference antigen values for the inhibitor have also been described.
Initial routine workup should include testing, as follows:
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Activated partial thromboplastin time (aPTT)
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Prothrombin time (PT)
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Thrombin-coagulable fibrinogen levels
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Euglobulin lysis time
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Whole blood clot lysis time
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Platelet counts and bleeding times (only if patient has not had antiplatelet drugs in the preceding 5-7 d)
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Platelet function
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Screening for factor XIII deficiency using a urea or monochloroacetic acid solubility test
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Thrombin time
Specialized laboratory tests are as follows:
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Alpha2-PI levels: Evaluate alpha2-PI levels with the use of antigenic and functional assays. Perform functional assays with both biologic and chromogenic tests. In addition, evaluate for a genetic defect in collaboration with a specialized laboratory.
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Tissue plasminogen activator (tPA) antigen and activity levels
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Plasminogen functional activity levels
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Levels of other inhibitors: These include alpha2-macroglobulin, alpha1-antitrypsin, alpha1-chymotrypsin inhibitor, C1 inactivator of complement, and antithrombin
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The role of alpha2-plasmin inhibitor (alpha2-antiplasmin) in fibrinolysis.
