Summary
A method for the measurement of heparin utilising the potentiating effect of heparin
on the action of anti-factor Xa is described. The effect on the assay of platelet
contamination of plasma, the presence of fibrinogen degradation products and low levels
of anti-factor Xa have been studied. The assay method has been compared with the calcium
thrombin time method and a group of obstetrical patients have been studied using both
methods.