INR derivation with the PT/INR Line simplified using a spreadsheet from the world wide web.

Area of Science:

• Clinical Chemistry
• Hematology
• Medical Diagnostics

Background:

• The Prothrombin Time/International Normalised Ratio (PT/INR) Line method, validated using five European Concerted Action on Anticoagulation (ECAA) certified plasmas, is reliable.
• A simpler INR derivation method, avoiding linear regression, is advantageous for laboratory use.

Purpose of the Study:

• To introduce a simplified method for deriving the international normalized ratio (INR).
• To enable laboratories to calculate INR without complex linear regression analysis.

Main Methods:

• Local PT/INR Lines were determined.
• A readily available internet spreadsheet was utilized for INR derivation, eliminating the need for additional calculations by laboratories.
• The method was tested across 16 centers using various coagulometers and human thromboplastin international reference preparations (IRPs).

Main Results:

• The procedure successfully derived INR values without requiring manual PT testing.
• It eliminated the need for local international sensitivity index calibration.
• The method does not necessitate the availability of thromboplastin IRPs or local mean normal prothrombin time.

Conclusions:

• INR values for local PT results can be easily obtained from the PT/INR Line using an Excel spreadsheet.
• This method simplifies INR derivation by avoiding complex linear regression analysis.
• The provided spreadsheet is accessible via a website for laboratory use.