For impedance method of aspirin analysis, which anticoagulant is recommended?

• A. Hirudin
• B. Heparin
• C. Citrate
• D. EDTA

Answer: (A)

Impedance-based platelet aggregation measures how platelets respond to activators in whole blood, so the anticoagulant must stop clotting without altering platelet function. For aspirin analysis, we look at how platelets respond to an agonist like arachidonic acid, which reveals aspirin’s effect on thromboxane A2 production. Hirudin fits this need because it directly inhibits thrombin to prevent clotting but does not interfere with calcium signaling or platelet activation pathways. This lets the impedance readout reflect true platelet function and the actual impact of aspirin.

Citrate binds calcium, a key player in platelet activation, which can blunt or distort aggregation responses and the aspirin effect. EDTA strongly chelates calcium and disrupts platelet function, making it unsuitable for aggregation testing. Heparin can introduce variability in platelet function measurements and may affect the impedance signal, reducing reliability.