LETTER
Monitoring Heparin Therapy
Robert Raschke, MD, and
Brendan Reilly, MD
15 January 1994 | Volume 120 Issue 2 | Pages 169-170
TO THE EDITOR:
We agree with the conclusions of Brill-Edwards and colleagues [1] regarding the establishment of a therapeutic range for heparin. Some institutions, however, might not have the resources to establish a therapeutic activated partial thromboplastin time (aPT) range using heparin levels. Also, care should be taken in adopting one of the reported therapeutic ranges. Specifically, the Dade reagent studied by Brill-Edwards and colleagues (Dade Actin FS; Baxter Diagnostics, Inc., Mississauga, Ontario, Canada) is much more sensitive and will yield a much higher therapeutic range than the reagent most commonly used in the United States (plain Dade Actin) [2]. We established the therapeutic range for plain Dade Actin by determining simultaneous aPT and heparin levels on plasma samples from 154 patients. Multiple linear regression analyses showed a therapeutic range of 49 to 69 seconds (mean control value, 25 seconds).
Institutions that use plain Dade Actin and that cannot customize their own therapeutic range might consider adopting a therapeutic range of 50 to 70 seconds. Unless the sensitivity of this reagent changes dramatically, this range is likely to be more accurate than a range of 1.5 to 2.5 times the control aPT (approximately 38 to 63 seconds) and would tend to reduce the frequency of subtherapeutic anticoagulation with its attendant risk for recurrent thromboembolism [3].
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Author and Article Information
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Good Smaritan Regional Medical Center; Phoenix, AZ 85006
1. Brill-Edwards P, Ginsberg JS, Johnston M, Hirsh J. Establishing a therapeutic range for heparin therapy. Ann Intern Med. 1993; 119: 104-9.
2. College of American Pathologists. 1992 CAP Surveys, Set CG2-A. Northbrook, Illinois. College of American Pathologists; 1992:4-8.
3. Hirsh J. Drug therapy: heparin. N Engl J Med. 1991; 324:1565-74.
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