Indicated when the PTT is prolonged in the absence of heparin.
The test is preceded by a thrombin time to detect the presence of heparin or a direct thrombin inhibitor.
The patient’s plasma is mixed with normal plasma and the mixture is incubated and the PTT is repeated: if the PTT does not correct, the presence of an inhibitor may be present.
If the mixture does not correct inhibitors may be present to include: anti factor VIII or lupus anticoagulants.
If the study corrects a consideration for a coagulation factor deficiency may be present.