Vacuum blood collection tubes for plasma contain heparin salts which are applied to the internal walls of the tube (heparin content: 12-30 IU/mL of blood). As an anticoagulant, heparin activates antithrombins and blocks the clotting cascade in the blood sample. Acti-Fine ® tubes for collecting plasma are used in a wide range of biochemical, immunochemical, serologic, and immunohematology tests.