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Answering of question no. 7 with explaination

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Question 7 - Answer: B. A defective platelet function

The Clinical Findings

ParameterPatient's ValueNormal Range
Platelet count212,000/µL150,000 - 450,000/µL
Bleeding time12 minutesUp to 8-9 minutes
  • Platelet count = NORMAL (212,000/µL falls well within the 150,000-450,000/µL range)
  • Bleeding time = PROLONGED (12 minutes, when normal is up to ~8-9 minutes)

Why the Answer is B

The key principle here is the dissociation between platelet count (quantity) and bleeding time (quality/function):
"A prolonged bleeding time with a normal platelet count implies a qualitative platelet defect."
  • Morgan & Mikhail's Clinical Anesthesiology
Bleeding time is a test of platelet function, not of platelet number. It measures how well platelets can form a primary platelet plug at a wound site. When the count is normal but bleeding time is prolonged, the platelets are present in sufficient numbers but they are not functioning properly.

Why the Other Options Are Wrong

  • A. A decrease in platelet production - This would cause a LOW platelet count. The patient's count is 212,000/µL, which is completely normal, so production is adequate.
  • C. An increase in platelet production - The count is normal, not elevated (thrombocytosis would be >450,000/µL). There is no evidence of increased production.
  • D. A lower-than-normal platelet count - This is directly contradicted by the data. 212,000/µL is within the normal range of 150,000-450,000/µL.

What Causes Defective Platelet Function?

Common causes of a normal platelet count + prolonged bleeding time include:
  1. Aspirin / NSAIDs - Inhibit cyclooxygenase, blocking TXA2 production needed for platelet aggregation
  2. Von Willebrand disease - Deficiency of vWF, which is needed to link platelets to damaged endothelium
  3. Glanzmann's thrombasthenia - Deficiency of glycoprotein IIb/IIIa (fibrinogen receptor)
  4. Bernard-Soulier syndrome - Deficiency of glycoprotein Ib (vWF receptor)
  5. Uremia - Uremic toxins impair platelet adhesion and aggregation
The correct answer is B - A defective platelet function, because the patient has a normal platelet COUNT but a prolonged bleeding TIME, which classically indicates a qualitative (functional) platelet defect.
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