An analysis of the one-stage prothrombin time

Area of Science:

• Clinical Chemistry
• Hematology
• Coagulation Science

Background:

• The one-stage prothrombin time (PT) is crucial for monitoring anticoagulant therapy and assessing hemostasis.
• Variability in PT results can arise from differences in thromboplastin sensitivity to the protein induced by vitamin K absence (Pivka) inhibitor.
• Standardization of PT assays is essential for reliable clinical interpretation.

Purpose of the Study:

• To evaluate the performance of one-stage PT assays using thromboplastins with differing sensitivities to the Pivka inhibitor.
• To determine optimal sample handling and testing conditions for accurate and precise PT measurements.
• To assess the utility of a packed cell volume (PCV) correction method for standardizing PT results.

Main Methods:

• Analysis of one-stage PT using highly sensitive (Thrombotest) and slightly sensitive (Normotest) thromboplastins.
• Testing of whole blood and plasma samples with a 0.1 mol/l Na3 citrate dilution.
• Evaluation of sample size effects on coagulation activity and precision.
• Application and comparison of a PCV correction method.

Main Results:

• A one-tenth blood dilution with citrate was effective across a wide range of packed cell volumes (PCV).
• Both whole blood and plasma were suitable, with accuracy and precision enhanced by adjusting sample size based on coagulation activity.
• The PCV correction method proved superior by accounting for thromboplastin-specific Pivka inhibitor sensitivities.

Conclusions:

• The PCV correction method offers a preferable approach for standardizing one-stage PT assays.
• Optimizing sample handling and considering thromboplastin sensitivity are key to reliable PT measurements.
• This study provides insights into improving the accuracy and precision of PT testing in clinical practice.