Systematic bias in point-of-care INR testing: comparative analysis of Abbott and Roche devices.

OBJECTIVES

Point-of-care (POC) International Normalised Ratio (INR) testing provides rapid anticoagulation monitoring. Still, it is susceptible to systematic bias, particularly at supratherapeutic levels, which can lead to inappropriate warfarin dose adjustments and increased thrombotic risk. This study evaluated bias trends between Abbott and Roche POC INR devices.

METHODS

Bias trends were assessed using Royal College of Pathologists of Australasia Quality Assurance Programs survey data (2023-2025), in-house verification, and patient sample comparisons against laboratory instrument testing used as a comparative reference mark (Werfen ACL TOP).

RESULTS

Abbott PT INR cartridges demonstrated a shift from negative bias in 2023 to pronounced positive bias in 2024, with discrepancies most evident at INR >4.0. The introduction of Abbott PT Plus cartridges in 2025 significantly reduced bias, achieving near alignment with Roche CoaguChek Pro II and laboratory methods tested in this study. Comparative reagent analysis highlighted the influence of thromboplastin source and ISI values on harmonisation.

CONCLUSIONS

Findings reinforce the need for confirmatory venous testing when POC INR exceeds critical thresholds, and emphasise the importance of ongoing performance monitoring, structured escalation policies, and transparent communication with manufacturers.