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Rapid Point-of-Care Assay of Enoxaparin Anticoagulant Efficacy in Whole Blood
Published on: October 12, 2012
Establishing a therapeutic range for heparin therapy
P Brill-Edwards1, J S Ginsberg, M Johnston
1McMaster University Medical Center, Hamilton, Ontario, Canada.
Annals of Internal Medicine
|July 15, 1993
Summary
Determining therapeutic ranges for activated partial thromboplastin time (aPTT) requires considering reagent variability. Using protamine titration heparin levels provides a practical standard to ensure consistent unfractionated heparin dosing.
Area of Science:
- Clinical Chemistry
- Pharmacology
Background:
- Activated partial thromboplastin time (aPTT) is crucial for monitoring unfractionated heparin therapy.
- Variability in aPTT reagents complicates establishing a universal therapeutic range.
- Protamine titration offers a method to quantify heparin levels directly.
Purpose of the Study:
- To compare two methods for determining the therapeutic range of aPTT.
- To assess the reliability of aPTT ratios versus direct heparin level measurements.
Main Methods:
- Cohort study design in a referral teaching hospital.
- Inclusion of inpatients receiving intravenous unfractionated heparin for venous thromboembolic disease.
- Comparison of aPTT ratios (1.5-2.5x control) against protamine titration heparin levels (0.2-0.4 U/mL).
Main Results:
- An aPTT ratio of 1.5x control was significantly lower than the target protamine titration heparin level of 0.2 U/mL for all reagents tested.
- Substantial variation exists in aPTT reagent response to heparin, leading to different therapeutic ranges.
- Manufacturer and lot-specific variations in aPTT reagents were observed.
Conclusions:
- Heparin dosage must be adjusted based on the specific aPTT reagent used to achieve a target ratio.
- Establishing a therapeutic range using protamine titration heparin levels (0.2-0.4 U/mL) is practical.
- This approach compensates for reagent-dependent variations in aPTT response to heparin.
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