The anticoagulant of choice for performing coagulation studies is -
EDTA
Heparin
Tri sodium citrate
Double oxalate
The most commonly use anticoagulant for in vitro Coagulation Studies is Citric Acid.It is generally employed in the form of Sodium Citrate.
In Vitro use of anticoagulants

For coagulation studies-Sodium Citrate
For Hematological studies-EDTA
For estimation of ESR


Wintrobes method-Double oxalate.
Westergren method-Sodium Citrate.