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Relationship between total prothrombin, native prothrombin and the International Normalized Ratio (INR)
1Organon Teknika Corporation, Durham, NC 27704.
Thrombosis and Haemostasis
|August 3, 1992
Summary
Native prothrombin levels closely correlate with INR, offering a sensitive marker for monitoring oral anticoagulant therapy. This assay may help identify optimal therapeutic ranges.
Area of Science:
- Biochemistry
- Hematology
- Pharmacology
Background:
- Oral anticoagulant therapy requires careful monitoring using prothrombin time (PT) assays.
- International Normalized Ratio (INR) is a standardized measure of PT, but its correlation with specific prothrombin forms needs further investigation.
Purpose of the Study:
- To compare plasma levels of total prothrombin, native prothrombin, and des-carboxy-prothrombin with PT/INR results in patients on oral anticoagulants.
- To determine the most sensitive prothrombin marker for monitoring anticoagulant therapy.
Main Methods:
- Measurement of plasma total prothrombin, native prothrombin, and des-carboxy-prothrombin concentrations.
- Correlation analysis with International Normalized Ratio (INR) values in anticoagulated patients.
Main Results:
- Native prothrombin levels showed the strongest inverse correlation with INR (r = 0.89).
- Native prothrombin decreased significantly with increasing INR, reaching low levels at higher INR values.
- Des-carboxy-prothrombin levels increased with INR.
Conclusions:
- Native prothrombin antigen assay is a sensitive indicator for monitoring oral anticoagulant therapy, especially at lower doses.
- The strong relationship between native prothrombin and INR aids in defining appropriate therapeutic ranges for anticoagulation.