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Systematic bias in point-of-care INR testing: comparative analysis of Abbott and Roche devices
Sandya Arunachalam1, Tony Badrick1, Emmanuel J Favaloro2,3,4,5
1Royal College of Pathologists of Australasia Quality Assurance Programs (RCPAQAP), St Leonards, NSW, Australia.
Clinical Chemistry and Laboratory Medicine
|July 9, 2026
Summary
Point-of-care (POC) International Normalized Ratio (INR) testing bias varies between devices. Abbott devices showed increasing bias, especially above INR 4.0, necessitating confirmatory testing and manufacturer communication.
Area of Science:
- Clinical Chemistry
- Hematology
- Medical Device Technology
Background:
- Point-of-care (POC) International Normalized Ratio (INR) testing offers rapid anticoagulation monitoring but is prone to systematic bias.
- Bias, particularly at supratherapeutic INR levels, can lead to incorrect warfarin dosing and elevated thrombotic risk.
Purpose of the Study:
- To evaluate bias trends between Abbott and Roche POC INR devices.
- To assess the impact of device evolution and reagent characteristics on INR measurement harmonization.
Main Methods:
- Analysis of Royal College of Pathologists of Australasia Quality Assurance Programs survey data (2023-2025).
- In-house verification and patient sample comparisons against a laboratory reference instrument (Werfen ACL TOP).
Main Results:
- Abbott PT INR cartridges exhibited a trend from negative to significant positive bias (2023-2024), most pronounced at INR >4.0.
- New Abbott PT Plus cartridges (2025) demonstrated reduced bias, aligning closely with Roche CoaguChek Pro II and laboratory methods.
- Reagent analysis identified thromboplastin source and ISI values as key factors influencing measurement harmonization.
Conclusions:
- Confirmatory venous testing is crucial when POC INR results exceed critical thresholds.
- Continuous device performance monitoring, clear escalation protocols, and open communication with manufacturers are essential for ensuring patient safety.
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When assessing blood pressure (BP), healthcare professionals must consider various factors and potential unexpected outcomes to ensure accurate readings and provide proper patient care. Adhering to these guidelines is essential to achieving the most reliable results.
Monitoring Both Arms:
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Monitoring BP in both arms during the initial assessment is advisable, as the systolic value may differ by five to ten mm Hg between arms. For subsequent BP assessments, use the arm with the higher reading.