A FEW CLUES IN INTERPRETING AN ISOLATED PROLONGATION OF ACTIVATED PARTIAL THROMBOPLASTIN TIME (aPTT)

👆🏿aPTT tests the intrinsic and common pathways of coagulation 

👆🏿Though it is included commonly as a part of coagulation profile assessment, it's primary uses are to detect coagulation factor deficiency and titration of heparin therapy

👆🏿An isolated elevation of aPTT may indicate 

➖deficiency of Factor VIII or IX or XI or XII

➖acquired clotting factor inhibitors 

➖presence of Lupus anticoagulant 

👆🏿N.B.:- Factor VIII deficiency is Haemophilia A, Factor IX deficiency is Haemophilia B and Factor XI deficiency is Haemophilia C

👆🏿If factor levels are >30% of normal, aPTT may remain normal, for e.g. in mild von Willebrand disease [raised aPTT + prolonged Bleeding Time (BT)], in mild hemophilia etc

Reference: Martlew V. Peri-operative management of patients with coagulation disorders. Br J Anaesth. 2000; 85(3): 446–455.