Abstract
Measurement of the anticoagulant effect of non–vitamin K antagonist oral anticoagulants
(NOAC) may be desirable, in particular in patients with acute medical conditions.
Useful methods should give results rapidly within minutes, should be easy to perform,
specific, and sensitive. Using plasma samples, chromogenic assays can be made to be
specific for the two types of NOAC (factor Xa and thrombin inhibitors), and also hemoclot
and ecarin clotting time specific for dabigatran. If plasma samples anticoagulated
with sodium citrate are not available, blood samples anticoagulated with ethylene
diamine tetraacetic acid or serum samples may be regarded as alternatives for the
determination of NOAC. At present, dabigatran cannot be determined from serum samples
because it may be consumed during the clotting process to obtain serum. NOAC can be
determined in urine samples due to their renal elimination. Quantitative methods are
preferable to qualitative methods, although the latter may be advantageous in some
situations, being developed as point-of-care tests for oral factor Xa and thrombin
inhibitors. In these tests, the presence and absence of NOAC in urine can be identified
with the naked eye after a few minutes and these tests are highly specific and sensitive.
New assays such as a semiquantitative determination in urine samples and measurement
using other sample matrices are currently under development.
Keywords
direct factor Xa inhibitors - direct thrombin inhibitors - new oral direct anticoagulant
- serum - urine - plasma - chromogenic substrate methods
