Heparin
(anti-Xa) assay
Specimen requirements:
Fresh whole blood collected in
sodium citrate at a 9:1 ratio of blood to anticoagulant
Function:
Heparin binds with antithrombin III
and acts to inhibit the following:
Tested within 2 hours @ refrig or
stored at -20oC for 1 month
Xa, IXa, XIIa, and
thrombin
Principle:
Chromogenic method based on the
level of heparin that binds added factor Xa. Free Xa will react with substrate forming a colored complex.
Higher the heparin the
less color produced