Simplified Method for Local Correction of System International Normalized Ratio.

Area of Science:

• Clinical Chemistry
• Hematology
• Medical Diagnostics

Background:

• International Normalized Ratio (INR) calculation relies on the thromboplastin's International Sensitivity Index (ISI).
• Variability in ISI exists across different instruments and reagents, impacting INR accuracy.
• Standardized INR derivation is crucial for consistent clinical interpretation.

Purpose of the Study:

• To assess the effectiveness of a correction factor in refining INR calculations.
• To determine if a standardized correction method can improve INR accuracy.
• To evaluate the clinical utility of a corrected INR value.

Main Methods:

• Prothrombin time (PT) and INR were measured in patients using three thromboplastins with differing ISI values.
• A specific correction factor was applied to the initially derived INR values.
• The resulting corrected INR was compared against the observed INR.

Main Results:

• The application of the correction factor resulted in a range of differences between corrected and observed INR values, from -0.8 to 0.96.
• This indicates a significant adjustment potential for INR values based on the applied factor.
• The study demonstrates the variability in observed INR values and the impact of ISI.

Conclusions:

• The corrected INR is determined exclusively by prothrombin time (PT).
• This correction method is universally applicable to all patients, regardless of the reason for elevated PT.
• The findings suggest a more robust and consistent method for INR reporting in clinical practice.