Platelet Immunology Laboratory

Definition of Terms

Types of Measurements

  • Direct Test: Detection of antibodies bound to patient’s platelets.
  • Indirect Test: Detection of antibodies in patient’s plasma by incubating the plasma with allogeneic platelets.

Platelet Antibody Assays

  • Flow Cytometry Assay: A flow cytometer uses fluorescent antibodies to detect IgG or IgM antibodies bound to autologous or allogeneic platelets.

Platelet Antigen Determination

  • DNA Typing: This test uses the polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) to determine the genetic code variations responsible for the different platelet antigens (HPA-1 through HPA-6).
  • Platelet Antibody Determination (MAIPA): An enzyme linked assay (ELISA) performed by either using donor platelets of known platelet types to determine the specificity of platelet antibodies or a commercially available kit.

Heparin Antibody Assay

  • Heparin-Platelet Factor 4 Assay: Enzyme linked assay using a complex of heparin and platelet factor 4 (PF4) to capture antibody developed during type II heparin-induced thrombocytopenia (HIT).

ADAMTS-13 Protease Activity

  • ADAMTS -13 Protease Activity is measured by a Fluorescence Resonace Transfer (FRET) Assay in which fluorescence is detected when a synthetic von Willebrand Factor peptide (VWF73) is cleaved by ADAMTS13. Inhibitor activity is determined by measuring the ability of heat treated patient plasma to inhibit ADAMTS13 in normal plasma; inhibitor activity is expressed as percent inhibition of the ADAMTS13.

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