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Question 330
Physiology → Haematology
Classification
Question
SSBAOptions
Explanation
Abnormalities of factors VII, X, V and II prolong PT. Abnormalities of factors II, V, VIII, IX, X, XI and XII prolong APTT. Factor II therefore appears in both groups and participates in the common coagulation pathway.
Option Validity
A) Factor XII is associated with prolongation of APTT but not PT. It therefore does not satisfy the requirement that both tests are prolonged.
B) Factor XI is associated with prolongation of APTT but not PT. It therefore does not satisfy the shared requirement.
C) Factor VIII deficiency affects the intrinsic pathway and is associated with haemophilia A. It prolongs APTT rather than satisfying the requirement for prolongation of both tests.
D) Factor IX is associated with prolongation of APTT but not PT. It therefore does not satisfy the requirement that both tests are prolonged.
Further Reading
Saxena. Textbook for MRCOG-1. Physiology - Haematology - Prothrombin Time and Activated Partial Thromboplastin Time, p.72.