Quantitative one-stage assays for factors V and X

Area of Science:

• Hematology
• Clinical Chemistry
• Coagulation Science

Background:

• Standard laboratory assays for blood coagulation factors V and X include prothrombin time (PT), Russell's viper venom time (RVVT), and activated partial thromboplastin time (aPTTT).
• The relative sensitivities of these assays for quantifying factors V and X are not consistently applied in clinical practice.

Purpose of the Study:

• To determine the relative sensitivities of PT, RVVT, and aPTTT in one-stage quantitative assays for factor V and factor X.
• To identify the optimal assay for accurate quantitation of factor V and factor X.

Main Methods:

• Quantitative one-stage assays were performed for factor V and factor X.
• Sensitivity was defined and measured as the slope of the reference curve for each assay.
• Relative sensitivities of PT, RVVT, and aPTTT were compared for both factors.

Main Results:

• Prothrombin time demonstrated the highest sensitivity for factor X and the lowest for factor V.
• Russell's viper venom time showed the highest sensitivity for factor V and the lowest for factor X.
• Activated partial thromboplastin time exhibited sensitivity comparable to RVVT for factor V and intermediate sensitivity for factor X.

Conclusions:

• Factor V is most accurately quantified using Russell's viper venom time.
• Factor X is most accurately quantified using prothrombin time.
• Current customary practices for quantifying factors V and X using these assays should be revised based on demonstrated sensitivities.