Factor deficiency (ie hemophilia)
Treat with FFP or protamine
Fibrinogen deficiency (ie DIC)
Treat with cryoprecipitate
Thrombocytopenia, platelet dysfunction (ie patient on clopidogrel)
Treat with platelets or DDAVP
Rapid clot lysis (ie tPA given)
Treat with TXA
Thromboelastography 
Age adjusted D-dimer
D-dimer
Ankle-brachial index
Capnography
Bubble study
Modified Wells Score
DVT ultrasound