Patrick Brill-Edwards, MD; Jeffrey S. Ginsberg, MD; Marilyn Johnston, ART; Jack Hirsh, MD
To compare two methods of determining a therapeutic range of activated partial thromboplastin time (aPT) results.
Referral teaching hospital.
Inpatients who received unfractionated heparin intravenously for venous thromboembolic disease.
A therapeutic range determined by aPT ratios of 1.5 to 2.5 times the control value as compared with a therapeutic range determined by protamine titration heparin levels of 0.2 to 0.4 U/mL.
For all aPT reagents studied, a ratio of 1.5 times the control value is much less than a minimum protamine titration heparin level of 0.2 U/mL. Various manufacturers' aPT reagents and reagent lots from the same manufacturer show considerable variation in response to heparin and therefore have different therapeutic ranges.
A different dose of heparin would be required to produce an aPT ratio of 1.5 times the control value, depending on the reagent used. Establishing a therapeutic range for aPT results using protamine titration heparin levels of 0.2 to 0.4 U/mL as a reference standard is practical and compensates for the variable response of aPT reagents to heparin.
Brill-Edwards P, Ginsberg JS, Johnston M, Hirsh J. Establishing a Therapeutic Range for Heparin Therapy. Ann Intern Med. ;119:104–109. doi: 10.7326/0003-4819-119-2-199307150-00002
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Published: Ann Intern Med. 1993;119(2):104-109.
Hospital Medicine, Venous Thromboembolism.
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Print ISSN: 0003-4819 | Online ISSN: 1539-3704
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