Increased concentrations of heparin cofactor II in diabetic patients, and possible effects on thrombin inhibition assay of antithrombin III.

Abstract

We compared concentrations of antithrombin III (AT-III) in plasma, as determined by an immunological method and by a functional thrombin inhibition method, in the presence of heparin in 160 blood samples from Type I diabetics. Although the correlation was highly significant (P less than 0.001) between the results obtained by the two methods, our data demonstrated that results by the thrombin inhibition assay, 121 (SD 15)%, expressed as percentages of the results for a normal plasma pool, were significantly (P less than 0.001) higher than by the immunoreactive method, 104 (SD 15)%, indicating an overestimation of functionally active AT-III. Concentrations of functionally active AT-III determined by a factor Xa inhibition assay, 105 (SD 13)%, were in the same range as immunoreactive AT-III. Addition of IgG antiserum to normal pooled plasma quenched only about 90% of the AT-III activity determined by the thrombin inhibition assay, but all of the AT-III activity determined by a factor Xa inhibition assay. These results demonstrate that the factor Xa inhibition assay is more specific for the determination of AT-III than the thrombin inhibition assay. We suggest that the high concentrations of heparin cofactor II, 117 (SD 17)%, might have caused an overestimation of AT III in this group of patients with diabetes Type I, and should not be overlooked in other clinical situations.

Anticoagulant Properties of Rabbit Lungs in Tissue Thromboplastin-induced Intravascular Coagulation

“…Protein C was measured by a chromogenic substrate method on a Cobas Mira analyzer (Hoffmann-La Roche, Basel, Switzerland) using commercially available kits (Chromogenix, Mglndal, Sweden). Antithrombin was determined by a FXa inhibition chromogenic substrate method (Chromogenix), which is not significantly affected by heparin cofactor I1 (13). A pool of rabbit plasma was used as calibrator, and the results for protein C and antithrombin were expressed as percentages relative to that pool.…”

Thrombin-Based Antithrombin Assays Show Overestimation of Antithrombin III Activity in Patients on Heparin Therapy due to Heparin Cofactor II Influence

“…A significant influence of HC II in an AT III assay based upon inhibition of bovine thrombin has also been shown for plasmas from Type I diabetic patients who had raised levels of HC II (20) and thus it is probable that any condition which causes release of intracellularlv stored HC II may result in overestimation of the AT III activity in a thrombin based assay.…”

Release of endothelium‐associated proteins into blood by injection of heparin in normal subjects and in patients with Type 1 diabetes

“…Antithrombin activity was analysed by a coagulation factor Xa inhibition assay performed on a Cobas Mira centrifugal analyser (Hoffman La Roche, Basel, Switzerland) and is expressed as decimal fraction of the level in a plasma pool (a.u.). This assay with EDTA plasma as sample medium has been demonstrated to be the most accurate assay for determination of antithrombin activity in diabetic patients [16]. Von Willebrand factor was determined by Imubind vWF ELISA kit (American Diagnostica Inc.).…”