Antithrombin
Department of Haematology
Notes
- For Antithrombin testing as part of a full Thrombophilia screen, please see the Thrombophilia Screen test page.
- Test performed at GRH
Antithrombin (AT, formerly Antithrombin III) is a serine protease inhibitor. AT's main physiological action is against Thrombin, and it also acts against Factor Xa to a lesser degree. Antithrombin exerts a powerful and immediate inhibitory action on Thrombin when Heparin is present. AT deficiency can be congenital or acquired. Hereditary deficiency is associated with spontaneous thrombo-embolic disease, and is believed to account for 2-4% of cases of unexplained thrombosis in young adults. Acquired deficiencies may occur in liver disease, DIC, pregnancy, in prolonged Heparin therapy, Asparaginase therapy and in women taking Oestrogen-containing contraceptives. Oral anticoagulation may cause a rise in AT levels.
The AT molecule has two binding sites, one for Thrombin and one for Factor Xa. Deficiency can be as a result of a defect at one or both of these sites (qualitative, Type II deficiency) or as a result of reduced levels of otherwise normal AT (quantitative, Type I deficiency).
Sample Requirements
For Antithrombin analysis alone:
3ml or 3.5ml Trisodium Citrate sample
Sample Storage and Retention
- Pre analysis storage: do not store, send to laboratory within 2 hours.
- Sample retention by lab: Citrate samples are retained for a minimum of 24 hours at 15-30°C. If specialist coagulation tests are requested, one or more aliquots may be frozen until analysis (or up to two months) at between -15 and -40°C. After analysis, these samples will be retained for a further 24 hours at 15-30°C.
This test can be added on to a previous request as long as there is sufficient sample remaining and the sample is less than 4 hours old.
Turnaround Time
Antithrombin testing only: within 4 weeks
Reference Range
Test | Reference Range | Unit |
---|---|---|
Antithrombin | 83 - 128 | % |