Determination of Antibody Activity by Platelet Aggregation

Area of Science:

• Hematology
• Immunology
• Clinical Diagnostics

Background:

• Platelets are crucial for hemostasis, but aberrant activation by pathogenic antibodies in immune thrombotic conditions leads to platelet aggregates, NETosis, thrombosis, and thrombocytopenia.
• Conditions like heparin-induced thrombocytopenia (HIT) and vaccine-induced thrombotic thrombocytopenia (VITT) involve pathogenic antibodies triggering platelet activation.

Purpose of the Study:

• To present light transmission aggregometry as a simple and reliable assay for assessing platelet function.
• To demonstrate the utility of light transmission aggregometry in detecting platelet-activating antibodies associated with HIT and VITT.

Main Methods:

• Light transmission aggregometry involves treating platelet-rich plasma (PRP) with patient sera or antibodies under stirring conditions.
• Platelet activation leads to aggregation, reducing plasma opacity and allowing increased light transmission, which is measured over time.
• This method is adapted from standard aggregometry protocols and does not require radioactive reagents.

Main Results:

• The assay quantifies platelet aggregation, providing a measure of antibody activity.
• Light transmission changes are proportional to the degree of platelet aggregation.
• The assay is technically less demanding and avoids radioactive reagents compared to other methods like 14C-serotonin release assay.

Conclusions:

• Light transmission aggregometry is a valuable, simple, and reliable assay for detecting platelet-activating antibodies in thrombotic conditions such as HIT and VITT.
• The protocol requires appropriate positive controls, including a weak HIT/VITT antibody and a physiological agonist, for accurate results.
• Using platelets from donors known to be reactive to HIT/VITT antibodies is essential to avoid false negatives.