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Standardization of coagulation tests.
1Department of Clinical Pathology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand.
Summary
Standardizing prothrombin time (PT) into the International Normalized Ratio (INR) has improved oral anticoagulant monitoring, though challenges remain. Activated partial thromboplastin time (APTT) standardization is ongoing, with proposed solutions for both tests.
Area of Science:
- Clinical Chemistry
- Hematology
- Medical Diagnostics
Background:
- Standardization of prothrombin time (PT) and activated partial thromboplastin time (APTT) is crucial for reliable laboratory results.
- PT monitoring of oral anticoagulants has been standardized using the International Normalized Ratio (INR), but faces challenges like coagulometer dependency and incorrect ISI values.
- APTT monitoring of heparin therapy is affected by various reagent and system factors, and its standardization is still in development.
Purpose of the Study:
- To review the progress and challenges in standardizing PT and APTT tests.
- To discuss proposed solutions for improving the accuracy and inter-laboratory consistency of INR calculations.
- To highlight the ongoing efforts and proposed candidates for APTT standardization.
Main Methods:
- Review of existing literature and standardization initiatives for PT and APTT.
- Analysis of the calibration models and reference preparations used for PT standardization (e.g., WHO IRP, INR system).
- Discussion of proposed solutions for INR system issues and advancements in APTT standardization, including candidate International Reference Preparations (IRPs).
Main Results:
- PT standardization has been successfully implemented through the INR system, converting local PT ratios using thromboplastin sensitivity (ISI) and International Reference Preparations (IRPs).
- Identified issues with the INR system include ISI dependency on coagulometers and potential inaccuracies in manufacturer-assigned ISI values.
- Several solutions are proposed for INR standardization, and a candidate IRP for APTT has been developed.
Conclusions:
- While PT standardization via INR has been largely successful, ongoing vigilance and addressing identified issues are necessary.
- APTT standardization is progressing, with proposed calibration models and candidate reference materials aiming to improve test reliability.
- Continued research and implementation of standardized methods are essential for accurate coagulation testing and patient management.