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Oral Surgery · single question

A patient with Hemophilia A needs a dental procedure. Which is the BEST diagnostic test to assess their clotting status?

  1. aPTT (activated partial thromboplastin time)
  2. Platelet count
  3. Bleeding time
  4. INR (International Normalized Ratio / PT)
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Correct answer: A. aPTT (activated partial thromboplastin time)

  • A. Correct. aPTT (activated partial thromboplastin time) measures the INTRINSIC coagulation pathway (factors VIII, IX, XI, XII, X, V, II). Hemophilia A (factor VIII deficiency) causes a prolonged aPTT with normal INR/PT.
  • B. Platelet count measures the number of platelets; Hemophilia A is a factor VIII deficiency (intrinsic pathway), not a platelet disorder.
  • C. Bleeding time (now largely replaced by PFA-100) evaluates platelet function, not clotting factor deficiencies.
  • D. INR/PT measures the EXTRINSIC and COMMON coagulation pathways (factors I, II, V, VII, X). Hemophilia A is an intrinsic pathway defect; INR is not sensitive to this.

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