Therapeutic decision analysis for monitoring UFH therapy using activated partial thromboplastin time compared with anti-Xa assay

Abstract

Aim At present, the traditional activated partial thromboplastin time (a-PTT) of 1.5–2.5 times the control value for monitoring unfractionated heparin (UFH) therapy continues to be used in the coagulation laboratory of Alexandria Main University Hospital. This study was conducted for the following reasons: to evaluate the relationship between heparin concentration and a-PTT results using Sysmex CA-1500; to define thea-PTT therapeutic range for our system; and to assess the level of agreement between a-PTT results and those obtained using the anti-Xa assay for monitoring UFH therapy. Results A significant positive correlation between a-PTT and anti-Xa assay results was noted (P=0.907, r=0.000, and P=0.098, r=0.000, for therapeutic a-PTT and therapeutic ratio, respectively). Regression analysis was carried out to determine the anti-Xa-derived therapeutic range (a-PTT results that correspond to a plasma heparin concentration of 0.3–0.7 U/ml by anti-Xa assay). The a-PTT therapeutic range was 64.4–107.93 s; the therapeutic range for the a-PTT ratio was 2.13–3.56 and that for the1.5–2.5 control method was 45.27–75.75 s. The agreement between the the a-PTT therapeutic range and the results of the anti-Xa assay was 78%, whereas the agreement between the 1.5–2.5 control method and the anti-Xa assay was 0.097%. Moreover, the potential for over therapeutic levels occurs more frequently with the 1.5–2.5 control method. Conclusion Anti-FXa-derived therapeutic range on Sysmex CA-1500 is superior to that obtained using the 1.5–2.5 control method in clinical decision making. Therapeutic ranges for various a-PTT reagent–coagulometer combinations could be provided by reagent manufacturers or central reference laboratories to the institutions that are not equipped to measure anti-Xa or to those for which the access to plasma samples from treated patients is limited.