What is The coagulation profile in a 13–year old girl with Menorrhagia having von Willebrand's disease is – and explain in detail?
Von Willebrand's factor acts as a plasma carrier of factor VIII and circulates in the blood as factor VIII-VWF complex. Its deficiency, therefore, impairs the intrinsic pathway of coagulation and prolongs the PTT as the intrinsic pathway of coagulation remains unimpaired, PT is not altered.

i) Bleeding time

It is a not a test for coagulation rather it tests the ability of the vessels to vasoconstrict and the platelets to form a hemostatic plug.
It is the time taken for a standardized skin puncture to stop bleeding.
Normal reference value is between 2-9 minutes.
Prolongation generally indicates the defect in platelet number or function.

ii) Prothrombin time (PT) 

This assay tests the extrinsic and common coagulation pathway.
So, a prolonged PT can result from a deficiency of factor V, VII, X, prothrombin or fibrinogen.

iii) Partial thromboplastin time (PTT) 

This assay tests the intrinsic and common coagulation pathways.
So, a prolonged PTT. Can results from the deficiency of factor V, VIII, IX, X, XI, XII, prothrombin or fibrinogen.

iv) Thrombin time

It is the time taken for clotting to occur when thrombin is added to the plasma.
It tests the conversion of fibrinogen to fibrin and depends on adequate fibrinogen level.
Prolonged thrombin time results from a decreased level of fibrinogen.