Medical Emergencies · single question
A patient takes both aspirin and clopidogrel. What laboratory or functional parameter is affected by this combination?
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Correct answer: D. Platelet function (aggregation), while the platelet count remains normal
- A. aPTT reflects the intrinsic cascade (heparin), also unaffected.
- B. The count is NOT reduced by antiplatelet drugs. A low count would suggest thrombocytopenia from another cause.
- C. PT/INR reflects the extrinsic coagulation cascade (warfarin), which these drugs do not affect.
- D. CORRECT. Both drugs impair platelet FUNCTION without reducing platelet NUMBER. Aspirin irreversibly acetylates COX-1, blocking thromboxane A2 production; clopidogrel irreversibly blocks the P2Y12 ADP receptor. The count on a CBC is normal — only aggregation studies or a platelet function assay would show the defect. Because the effect is irreversible, it lasts the 7–10 day platelet lifespan.
Note: ⚠️ NOTE: the recall keys this as 'platelet count.' That is incorrect — antiplatelet drugs change FUNCTION, not count. Worth correcting in the group. Bleeding time is prolonged; PT, aPTT, and count are all normal.
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