Low-dose aspirin irreversibly inhibits platelet cyclooxygenase-1. On platelet function testing, aggregation is impaired with which agonist?

• A Ristocetin
• B ADP at high dose
• C Arachidonic acid ✓
• D Collagen at high dose

Explanation

Aspirin acetylates COX-1, blocking conversion of arachidonic acid to thromboxane A2, so aggregation induced by arachidonic acid is abolished. High-dose ADP and collagen act through pathways independent of thromboxane and remain largely intact. Ristocetin tests von Willebrand factor mediated platelet agglutination via GPIb and is unaffected by aspirin.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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