Antithrombin level

Antithrombin has a powerful anticoagulant action in the presence of heparin, working by neutralising serine proteases, particularly thrombin and Xa. It acts more strongly against thrombin in the presence of higher molecular weight heparins, and against Xa with lower molecular weight heparins.

A hereditary deficiency of antithrombin is accompanied by a high frequency of spontaneous thrombotic disorders. Hereditary antithrombin deficiencies are quantitative (type I) or qualitative (type II). The incidence of inherited deficiency has been estimated at between 1:2,000 and 1:5,000 in the normal population. In addition, a number of acquired deficiencies have also been described.

An antithrombin antigen assay is available to distinguish between type I or type II where the antithrombin activity is abnormally low.

Venous thromboembolism at a young age (including childhood)
Recurrent venous thromboembolism
Unusual site of thrombosis (eg. mesenteric, renal, portal veins, cerebral venous sinuses)
Thrombosis during pregnancy or puerperium
Recurrent superficial thrombophlebitis
Arterial thrombosis at a young age (abruptio placentae, pre-term delivery)
Neonatal purpura fulminans or massive thrombosis in newborn
Perthe's disease of the lip Warfarin-induced skin necrosis.

Special handling: avoid prolonged stasis during venepuncture. Sample must be received by lab within 2 hours of collection. Samples will be rejected if under/over-filled, clotted or haemolysed or if patients are receiving anticoagulant therapy. Similarly, sampling is inappropriate within 4 weeks post-childbirth or during an acute phase inflammatory response. A discussion with a haematologist is advisable prior to requesting this and other thrombophilia tests. Requests may be subject to approval by haematology prior to testing.

Adult Reference Range:

Note: The reference ranges for use on patients over the age of 16 years, has been locally verified in accordance with CLSI Guideline EP28-A3c through evaluation on representative normal individuals across the sites to reflect our patient population.

Data sourced via Stago from:
Monagle P. et al. Thromb Haemost 2006; 95: 362-372.
Summerhayes R. et al. J Thromb Haemost, 2007; 5, Supp 2: P-M-105.
Summerhayes R. et al. J Thromb Haemost, 2007; 5, Supp 2: P-S-397.

Paediatric Reference Range

Note: Due to the complexity of collecting blood samples for analysis on normal neonates and paediatric patients, the reference ranges for use on patients up to 16 years of age have been taken from published data, from a research study using comparable methodology and equipment as that currently employed in our organisation. Please contact the laboratory for coagulation paediatric ranges.

Data sourced via Stago from:
Monagle P. et al. Thromb Haemost 2006; 95: 362-372.
Summerhayes R. et al. J Thromb Haemost, 2007; 5, Supp 2: P-M-105.
Summerhayes R. et al. J Thromb Haemost, 2007; 5, Supp 2: P-S-397.

The laboratory is not UKAS accredited for Antithrombin activity and Antithrombin antigen due to a change in equipment/assay. Awaiting assessment.

This test is not currently accredited