This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Haematology, Subject name: Pathology
Which of the following pathway does aPTT measure 
Select and explain. 
A. Intrinsic pathway, B. Extrinsic pathway, C. Both intrinsic and extrinsic, D. Complement pathway
B: Extrinsic pathway
Answer: B: Extrinsic pathway 
Explanation: activated paial thromboplastin time The paial thromboplastin time (PTT) or activated paial thromboplastin time (aPTT orAPTT) is a blood test that characterizes coagulation of the blood. A historical name for this measure is the kaolin-cephalin clotting time (KCCT), reflecting kaolin and cephalin as materials historically used in the test. Ref Robbins 9/e pg 450