Modification of an Amidolytic Heparin Assay to Express Protein-Bound Heparin and to Correct for the Effect of Antithrombin III Concentration

SummaryA modification of an anti-Xa assay for plasma heparin has been devised using a low molecular weight dextran sulfate that competitively binds protein heparin neutralizers and displaces masked heparin. The addition of 0.12 mg dextran sulfate per ml of plasma permits heparin, neutralized by the products of platelet aggregation, to recover full functional activity against Xa. The assay will permit a more accurate assessment of both exogenous plasma heparin and endogenous liepaiin-like activity in blood samples collected with varying techniques. A further modification is proposed employing polybrene to neutralize the plasma heparin-like material providing a concurrent control for each sample that increases accuracy by eliminating the effect of varying AT-III levels which have anti-Xa activity.

The Effect of Oral Contraceptives on Coagulation and Fibrinolytic Parameters in the Chinese – A Prospective Study

SummaryThirty-two Chinese and 7 Caucasians were studied prospectively for 12 months for the effects of oral contraceptives (OC) on certain coagulation and fibrinolytic parameters. In both ethnic groups there was an increase in α1 antitrypsin level. There was no significant change in antithrombin III concentration measured either by radioimmunoassay (At-III-RIA) or chromogenic assay (anti Xa-chromogenic) in the Chinese, but a significant decrease in anti Xa-chromogenic at 7 months and At-III-RIA at 12 months in the Caucasians. Also, α2 plasmin inhibitor (α2PI) levels were unchanged in the Chinese but a significant increase occurred in the Caucasians at 12 months. Enhanced fibrinolytic response to venous occlusion was demonstrated in the Chinese at 12 months but not in the Caucasians.