Should therapeutic range in heparin therapy be changed with new reagent for activated partial thromboplastin time?

Kim, Hee Jin; Cho, Han Ik; Lee, Dong Soon

Abstract

BACKGROUND
Heparin is widely used for various thromboembolic diseases. Although the range of 0.3~0.7 U/mL anti-Xa activity was established as a gold standard for monitoring unfractionated heparin treatment, activated partial thromboplastin time (aPTT) is commonly used. In Seoul National University Hospital, therapeutic aPTT ratio (patient's aPTT/control aPTT) with a range of 1.5~2.3 has been used with aPTT values with Dade Actin activated cephaloplastin reagent (Dade Behring, Marburg, Germany; reagent A; reference range, 23-32 sec). Changing the reagent, we established new reference range for aPTT and verified whether the therapeutic range in heparin therapy should be changed.
METHODS
Seventy-six subjects with normal coagulation function were selected as reference sample group. With aPTT values by STA -PTT Automate 5 reagent (Diagnostica Stago, Asnieres, France; reagent B) from this group, new reference range was established. On the other hand, clinical samples from another group of twenty-nine subjects under intravenous unfractionated heparin treatment was prepared for measuring aPTT both by reagent A and reagent B, concomitantly with anti-Xa activity and the relationships between the respective aPTT values and ratios against anti-Xa activity were analyzed.
RESULTS
Newly established reference range of aPTT by reagent B was 29~45 sec (mean +/- 2SD). The corresponding aPTT ranges to anti-Xa activity range of 0.3~0.7 U/mL for reagent A and reagent B were 49~60 sec and 87~118 sec, respectively. These ranges were equivalent to the aPTT ratios of 1.7~2.1 and 2.4~3.2, respectively.
CONCLUSION
Various reagents for measuring aPTT available nowadays varies greatly in their sensitivity. In that sense, the therapeutic range for the unfractionated heparin should be changed with the new reagent and the newly established reference range thereof. As for the STA -PTT Automate 5 reagent, our data showed that 2.4~3.2 aPTT ratio is recommended.