Screening Tests: Summary
The following table provides a summary of the results obtained using the PT, APTT, Fibrinogen and Thrombin Time in various disorders.
Factor XIII deficiency
Qualitative platelet disorder
Connective tissue problem e.g. Ehlers Danlos
Mild coagulation factor deficiency
|Normal||Normal||↑||Normal||Normal||FVIII, FIX, FXI or FXII deficiency
VWD - if the FVIII level is reduced
Lupus anticoagulant [Occasionally a very strong lupus anticoagulant or a lupus anticoagulant that has anti-prothrombin activity can result in a prolonged PT. Similarly a lupus anticoagulant can also be associated with thrombocytopaenia.]
Other contact factor deficiency
|Normal||↑||↑||Normal||Normal||'Common pathway' deficiency i.e. FII, FV or FX deficiency
Multiple clotting factor deficiencies e.g. combined FV and FVIII deficiency
Warfarin or vitamin K antagonist
Vitamin K deficiency or a mutation within one of the genes encoding key enzymes involved in VK metabolism.
Occasionally a very strong Lupus anticoagulant can cause these findings but it is unusual to see a prolongation of the PT with a LA due to the high concentration of PL used in the PT test.
|↓||Normal||Normal||Normal||Normal||Primary platelet problem e.g. ITP.
The Mean Platelet Volume [MPV] can be helpful in establishing the causes of thrombocytopaenia.
A raised MPV is often associated with increased peripheral destruction e.g. ITP - whereas a reduced MPV is often seen in association with bone marrow failure.
Changes in the MPV are also seen in patients with various inherited platelet disorders e.g. Wiskott Aldrich syndrome
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