Determination of tissue thromboplastin activity

Area of Science:

• Coagulation science
• Biochemistry
• Diagnostic assay development

Background:

• The one-stage prothrombin time (PT) test is commonly used to assess extrinsic pathway coagulation, but its reliability for quantifying thromboplastin activity is debated.
• Variability in clotting times and tube materials can significantly impact results, limiting its use for comparing different thromboplastin preparations.
• Accurate measurement of thromboplastin activity is crucial for understanding coagulation disorders and developing effective hemostatic agents.

Purpose of the Study:

• To evaluate the suitability of the one-stage prothrombin time test for quantifying thromboplastin activity.
• To develop and validate a more reliable two-stage assay for human thromboplastin.
• To compare the factor VII activating capacity of thromboplastin from different animal tissues.

Main Methods:

• Evaluation of the one-stage prothrombin time test using a correction method.
• Development of a two-stage assay employing purified human factor VII, a factor VII reagent, and a phospholipid suspension.
• Application of the correction method to the two-stage assay, plotting clotting times against the reciprocal of thromboplastin concentrations.

Main Results:

• The one-stage PT test demonstrated significant variability and was deemed unsuitable for quantitative comparisons of thromboplastin activity.
• The developed two-stage assay yielded a rectilinear dose-response curve, indicating reliability and reproducibility.
• Porcine tissue thromboplastin effectively activated human factor VII, whereas bovine tissue thromboplastin showed minimal activation.

Conclusions:

• The one-stage PT assay is inadequate for precise thromboplastin activity quantification due to intrinsic pathway interference.
• The novel two-stage assay provides a robust method for measuring human thromboplastin activity and its interaction with factor VII.
• Tissue source significantly influences thromboplastin's ability to activate human factor VII, with porcine tissue being more effective than bovine.