The Activated Partial Thromboplastin Time After Heparin Removal (aPTT/HR): The Basis Of A New Single Test Stratagem For Monitoring All Phases Of Anticoagulation With Heparin And/Or Coumarins

Safe and accurate monitoring of the transition from the antithrombotic protection afforded by the heparin-antithrombin III complex to that of coumarin modified zymogens has traditionally been provided by special dilutional one-stage prothrombin times. The demonstrated ability of ECTEOLA anion exchange columns to remove heparin from plasma containing acarboxy forms of the vitamin k dependent factors led to the development of an alternative test, the protime after heparin removal (PT/HR) (Am J Clin Pathol 71 (6): 665, 1979). Application of this same technology to the activated partial thromboplastin time (aPTT/HR) results in: 1) a superior alternative to dilutional and ion exchange protimes; and 2) a new single test/pathway scheme for following the heparin, heparin and coumarin, and coumarin phases of anti-coagulation therapy. The fitness of the aPTT for monitoring therapy with heparin alone and coumarins alone has been previously established. Preliminary studies indicate that the aPTT/HR is very similar in its ability to determine the adequacy of anticoagulation to a combination of the PT and aPTT. Comparison of the aPTT/HR with the PT/HR for combined heparin and coumarin monitoring indicated that it: 1) more closely approximates the functional activity of factor X; 2) is equally sensitive to heparin and coumarins; 3) is responsive to more common clinically significant depressions of factors; and 4) is the test of choice for pre-surgical screening.