Special Precautions/Comments:

Additional Information:

Forms part of the coagulation screen profile and is sensitive to deficiencies in Factors XII, XI, IX, VII, X, V, II and fibrinogen.
Possible causes of prolonged APTT

Deficiencies of factors XII, XI, IX & VIII – The APTT can be normal with mild deficiencies of these clotting factors. In general the deficient factor has to be less than 20-40% of normal before the APTT is prolonged.

Contact factor deficiency e.g. pre-kallikrein deficiency – In multiple clotting factor deficiencies the APTT becomes prolonged with less severe reductions in factor levels.

Acquired clotting factor inhibitors – these are most commonly directed against FVIII and may occur as either autoantibodies [e.g. acquired Haemophilia A] or alloantibodies (in individuals with severe Haemophilia A following exposure to exogenous factor VIII e.g. the use of factor VIII concentrate to treat a bleed). Inhibitors against other clotting factors are rare but do occur e.g. Factor V.

Lupus anticoagulant [LA] – LA targets phospholipid and can result in an isolated prolongation of the APTT.

Heparin / LMWH / Direct Thrombin Inhibitors / Direct Xa inhibitors – Heparin, heparinoids and DOACs may prolong APTT results. Unfractionated heparin, LMWH’s (including enoxaparin, tinzaparin, dalteparin) and Fondaparinux may prolong the APTT more than the other non-coumarin anticoagulants.

Special requirements:
Sample stable for 8 hours.
Sample must be filled to the line to ensure correct ratio of blood to anticoagulant, ensure adequate mixing.
Forms part of the coagulation screen profile and is sensitive to deficiencies in Factors XII, XI, IX, VII, X, V, II and fibrinogen.
Possible causes of prolonged APTT

Deficiencies of factors XII, XI, IX & VIII – The APTT can be normal with mild deficiencies of these clotting factors. In general the deficient factor has to be less than 20-40% of normal before the APTT is prolonged.

Contact factor deficiency e.g. pre-kallikrein deficiency – In multiple clotting factor deficiencies the APTT becomes prolonged with less severe reductions in factor levels.

Acquired clotting factor inhibitors – these are most commonly directed against FVIII and may occur as either autoantibodies [e.g. acquired Haemophilia A] or alloantibodies (in individuals with severe Haemophilia A following exposure to exogenous factor VIII e.g. the use of factor VIII concentrate to treat a bleed). Inhibitors against other clotting factors are rare but do occur e.g. Factor V.

Lupus anticoagulant [LA] – LA targets phospholipid and can result in an isolated prolongation of the APTT.

Heparin / LMWH / Direct Thrombin Inhibitors / Direct Xa inhibitors – Heparin, heparinoids and DOACs may prolong APTT results. Unfractionated heparin, LMWH’s (including enoxaparin, tinzaparin, dalteparin) and Fondaparinux may prolong the APTT more than the other non-coumarin anticoagulants.

Special requirements:
Sample stable for 8 hours.
Sample must be filled to the line to ensure correct ratio of blood to anticoagulant, ensure adequate mixing.
Forms part of the coagulation screen profile and is sensitive to deficiencies in Factors XII, XI, IX, VII, X, V, II and fibrinogen.
Possible causes of prolonged APTT

Deficiencies of factors XII, XI, IX & VIII – The APTT can be normal with mild deficiencies of these clotting factors. In general the deficient factor has to be less than 20-40% of normal before the APTT is prolonged.

Contact factor deficiency e.g. pre-kallikrein deficiency – In multiple clotting factor deficiencies the APTT becomes prolonged with less severe reductions in factor levels.

Acquired clotting factor inhibitors – these are most commonly directed against FVIII and may occur as either autoantibodies [e.g. acquired Haemophilia A] or alloantibodies (in individuals with severe Haemophilia A following exposure to exogenous factor VIII e.g. the use of factor VIII concentrate to treat a bleed). Inhibitors against other clotting factors are rare but do occur e.g. Factor V.

Lupus anticoagulant [LA] – LA targets phospholipid and can result in an isolated prolongation of the APTT.

Heparin / LMWH / Direct Thrombin Inhibitors / Direct Xa inhibitors – Heparin, heparinoids and DOACs may prolong APTT results. Unfractionated heparin, LMWH’s (including enoxaparin, tinzaparin, dalteparin) and Fondaparinux may prolong the APTT more than the other non-coumarin anticoagulants.

Special requirements:
Sample stable for 8 hours.
Sample must be filled to the line to ensure correct ratio of blood to anticoagulant, ensure adequate mixing.
Forms part of the coagulation screen profile and is sensitive to deficiencies in Factors XII, XI, IX, VII, X, V, II and fibrinogen.
Possible causes of prolonged APTT

Deficiencies of factors XII, XI, IX & VIII – The APTT can be normal with mild deficiencies of these clotting factors. In general the deficient factor has to be less than 20-40% of normal before the APTT is prolonged.

Contact factor deficiency e.g. pre-kallikrein deficiency – In multiple clotting factor deficiencies the APTT becomes prolonged with less severe reductions in factor levels.

Acquired clotting factor inhibitors – these are most commonly directed against FVIII and may occur as either autoantibodies [e.g. acquired Haemophilia A] or alloantibodies (in individuals with severe Haemophilia A following exposure to exogenous factor VIII e.g. the use of factor VIII concentrate to treat a bleed). Inhibitors against other clotting factors are rare but do occur e.g. Factor V.

Lupus anticoagulant [LA] – LA targets phospholipid and can result in an isolated prolongation of the APTT.

Heparin / LMWH / Direct Thrombin Inhibitors / Direct Xa inhibitors – Heparin, heparinoids and DOACs may prolong APTT results. Unfractionated heparin, LMWH’s (including enoxaparin, tinzaparin, dalteparin) and Fondaparinux may prolong the APTT more than the other non-coumarin anticoagulants.

Special requirements:
Sample stable for 8 hours.
Sample must be filled to the line to ensure correct ratio of blood to anticoagulant, ensure adequate mixing.
Forms part of the coagulation screen profile and is sensitive to deficiencies in Factors XII, XI, IX, VII, X, V, II and fibrinogen.
Possible causes of prolonged APTT

Deficiencies of factors XII, XI, IX & VIII – The APTT can be normal with mild deficiencies of these clotting factors. In general the deficient factor has to be less than 20-40% of normal before the APTT is prolonged.

Contact factor deficiency e.g. pre-kallikrein deficiency – In multiple clotting factor deficiencies the APTT becomes prolonged with less severe reductions in factor levels.

Acquired clotting factor inhibitors – these are most commonly directed against FVIII and may occur as either autoantibodies [e.g. acquired Haemophilia A] or alloantibodies (in individuals with severe Haemophilia A following exposure to exogenous factor VIII e.g. the use of factor VIII concentrate to treat a bleed). Inhibitors against other clotting factors are rare but do occur e.g. Factor V.

Lupus anticoagulant [LA] – LA targets phospholipid and can result in an isolated prolongation of the APTT.

Heparin / LMWH / Direct Thrombin Inhibitors / Direct Xa inhibitors – Heparin, heparinoids and DOACs may prolong APTT results. Unfractionated heparin, LMWH’s (including enoxaparin, tinzaparin, dalteparin) and Fondaparinux may prolong the APTT more than the other non-coumarin anticoagulants.

Special requirements:
Sample stable for 8 hours.
Sample must be filled to the line to ensure correct ratio of blood to anticoagulant, ensure adequate mixing.
Forms part of the coagulation screen profile and is sensitive to deficiencies in Factors XII, XI, IX, VII, X, V, II and fibrinogen.
Possible causes of prolonged APTT

Deficiencies of factors XII, XI, IX & VIII – The APTT can be normal with mild deficiencies of these clotting factors. In general the deficient factor has to be less than 20-40% of normal before the APTT is prolonged.

Contact factor deficiency e.g. pre-kallikrein deficiency – In multiple clotting factor deficiencies the APTT becomes prolonged with less severe reductions in factor levels.

Acquired clotting factor inhibitors – these are most commonly directed against FVIII and may occur as either autoantibodies [e.g. acquired Haemophilia A] or alloantibodies (in individuals with severe Haemophilia A following exposure to exogenous factor VIII e.g. the use of factor VIII concentrate to treat a bleed). Inhibitors against other clotting factors are rare but do occur e.g. Factor V.

Lupus anticoagulant [LA] – LA targets phospholipid and can result in an isolated prolongation of the APTT.

Heparin / LMWH / Direct Thrombin Inhibitors / Direct Xa inhibitors – Heparin, heparinoids and DOACs may prolong APTT results. Unfractionated heparin, LMWH’s (including enoxaparin, tinzaparin, dalteparin) and Fondaparinux may prolong the APTT more than the other non-coumarin anticoagulants.

Special requirements:
Sample stable for 8 hours.
Sample must be filled to the line to ensure correct ratio of blood to anticoagulant, ensure adequate mixing.