| Abstrakt: |
Most commercially available prothrombin (PT) assays are stated to be insensitive to heparin in therapeutic doses. These conclusions are, however based on studies using normal plasma samples. The aim of the present study was to study the effect of unfractioned heparin, three low molecular heparins, and a heparinoid on six prothrombin assays using plasma samples from patients on warfarin. Plasma samples from 30 patients on warfarin were heparinized in vitro with unfractioned heparin, three different low molecular weight heparins (Fragmin® [Pharmacia/Upjohn Inc., Delaware, U.S.A.], Klexane® [Rhone Poulenc Rorer, Halte, Demark], and Logiparin-Dinnohep®, [Leo Biological Products, Ballerup, Denmark]) and the herparinoid Org 10172 (Orgaran [Organon, Oss, the Netherlands]) to obtain 0.50-1.50 U/ml plasma. The PT time was then determined with four PT reagents stated to be insensitive to heparin (Innovin [Dade, Miami, Florida, U.S.A.], Nycoplastin [Nycomed Pharma, Oslo, Norway], Nycotest PT [Nycomed Pharma], and Stago Prothrombin Complex Assay [SPA 50, Diagnostica Stago, Franconville, France])and two reagents stated to be sensitive to heparin (Manchester Reagent [Manchester Comparative Reagent, Ltd., Stockport, Great Britain] and Thrombotest [Nycomed]). All PT assays except Innovin were sensitive to the heparins. With a heparin concentration of 0.5 U/ml plasma, the increase in INR ranged from 18-55% with Thrombotest and 0-44% with the other assays. The increase in INR values by 1.5 U/ml plasma differed among the heparins used: Manchester Reagent 6-297%, Thrombotest 43-247%, Nycoplastin 48-81%, SPA 50 20-74%, Nycotest PT 17-36% and Innovin0-5%. Orgaran did not prolong the clotting time with the Master Reagent. With the other five PT assays, Innohep (Leo Biological Products, Ballerup, Denmark) and Orgaran gave the largest increase in INR value. Fragmin, Klexane, and unfractioned heparin caused similar low increase in INR. A 3-h delay in testing prolonged the pr... [ABSTRACT FROM AUTHOR] |
