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Platelet Glycoprotein Antibody

Platelet Glycoprotein Antibody

Test Highlight

Platelet Glycoprotein Antibody

  

Clinical Use

  • Thrombocytopenia differential diagnosis

Clinical Background

Thrombocytopenia is caused by inherited disorders and immune or nonimmune-related acquired disorders. Platelet autoantibodies directed against intrinsic platelet antigens (glycoproteins), immune complexes, drug-protein immune complexes, or other antigens binding the platelet surface can help differentiate between immune and nonimmune disorders. Two methods are available for direct platelet antibody detection. The flow cytometry method is suggested as an initial screen due to its superior sensitivity; it detects any platelet-associated IgG immunoglobulins that may be present in immune or non-immune thrombocytopenia. Positive flow cytometry results should be confirmed with the more specific enzyme-linked immunosorbent assay (ELISA) which detects only glycoprotein-specific platelet antibodies (GP IIb/IIIa, GP Ib/IX, GP Ia/IIa) that are associated with immune thrombocytopenia.

Method

This ELISA utilizes microwell strips that have been coated with specific platelet glycoproteins (GP IIb/IIIa, GP Ib/IX and GP Ia/IIa). After eluting any platelet autoantibodies attached to the patient’s platelets, the eluate is incubated in 6 microwells, two for each glycoprotein. Bound antibodies are then detected colorimetrically. Results are reported as negative or positive for GP IIb/IIIa, GP Ib/IX or GP Ia/IIa.

Interpretive Information

A positive result indicates the presence of platelet antibodies bound to the platelet surface. Positive results are observed in patients with idiopathic thrombocytopenic purpura (ITP), systemic lupus erythematous (SLE), lymphoma, and HIV infection. Although antiplatelet antibodies are detected in 70% to 90% of patients with ITP, they are not deemed necessary for routine diagnosis.

A negative result suggests an alternative immune or nonimmune etiology in patients with thrombocytopenia.

Results from this test should be interpreted in context with all clinical and laboratory findings.

 

Content reviewed 02/2013

 
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