Comparison of Various Activated Partial Thromboplastin Reagents in the Laboratory Control of Heparin Therapy

Abstract

The activated partial thromboplastin time (APTT) is being used by an increasing number of laboratories to monitor heparin anticoagulation. Numerous commercial sources of partial thromboplastin are available. These are used in conjunction with one of three activators, (1) kaolin, (2) celite, or (3) ellagic acid, and with varying concentrations of calcium chloride. The current study was undertaken to evaluate several widely used commercial reagents to determine whether comparable results are obtained when reagent systems are interchanged. A plasma pool was prepared and aliquots of it were adjusted to contain specific heparin concentrations ranging from 0.0 to 1.2 units per ml. Each of these aliquots was tested with reagents from six different manufacturers, using Fibrometer methodology according to the manufacturers’ instructions. The results vary considerably according to the manufacturers’ products used in the performance of the test