Abstract
Vitamin K antagonists (VKA) have been used for many years as effective anticoagulant
therapy. The laboratory plays a crucial role in measuring the prothrombin time (PT)
and calculating the international normalized ratio (INR). Each component of the calculation
has the potential to increase error in the final result. This article discusses the
laboratory aspects of monitoring VKA including sample requirements, PT, determination
of the INR, point of care (POC) testing, external quality assurance/proficiency testing,
and reversal strategies for VKA therapy. The implementation of the PT/INR reporting
standard was a significant improvement in laboratory medicine. However, further room
for improvement exists in the management of PT/INR testing, to clarify the role of
POC testing and continue the harmonization process to ensure reliability and reproducibility
of INR results.
Keywords
laboratory - monitoring - vitamin K antagonists - prothrombin time - INR
