Avoid performing laboratory investigation of venous thromboembolism during the acute phase of thrombosis, since there could be a reduction in the levels of protein C, S, and antitrombin III: 90% agreement
The levels of protein C, S, antitrombin III (AT) can be lower in the acute phase of thrombosis, which not always represents a true deficiency. Other level that should not be checked in this phase is lupus anticoagulant test, which can be influenced by the therapeutic anticoagulant. Another important data is that, during pregnancy and when using contraception, there may be a false protein S deficiency.(6,7,16)
Therefore, one should avoid investigating VTE during the acute phase of thrombosis.
The best time to perform laboratory investigation of venous thromboembolism is at the end of anticoagulation, as of 2 to 4 weeks after discontinuing oral anticoagulation: 94% agreement
The ideal time for laboratory investigation is controversial in literature. We will follow the recommendation to perform it 4 weeks after the end of anticoagulant therapy, since this is the one most described in literature.(6,12,17)
Genetic tests for factor V Leiden and test of mutation of prothrombin, anticardiolipin, and anti-beta2-glycoprotein I do not suffer interference during the acute phase of thrombosis: 88% agreement
The dosages of genetic factors (FVL and mutation of prothrombin) or titers of antibodies (anticardiolipin and beta2-glycoprotein) can be done at any time, since they do not suffer interference of the acute phase of thrombosis or from the use of anticoagulants.(8,12,17)