If patient is being treated with heparin, this should be noted as heparin treatment may lower plasma antithrombin.
Submit sample (platelet poor plasma) in a plastic vial.
1. Centrifuge, remove plasma, and centrifuge plasma again.
2. Freeze plasma immediately (no longer than 4 hours after collection) at -20 degrees C or, ideally, < or =-40 degrees C.
1. Double-centrifuged specimen is critical for accurate results as platelet contamination may cause spurious results.
2. Each coagulation assay requested should have its own vial.
Antithrombin antigen results are potentially affected by:
-Heparin (unfractionated or low-molecular-weight) >4 U/mL
-Hemoglobin >7 g/L
-Bilirubin >500 mg/L
-Lipemia; may lead to an over-estimation of the antithrombin antigen level
-Rheumatoid factor (RF) >800 IU/mL; may lead to overestimation of the antithrombin antigen level
-Anti-rabbit antibodies in certain subjects leads to aberrant results
-Heparin therapy may temporarily decrease plasma antithrombin antigen into the abnormal range