Assessment of Commutability in Factor VIII Activity Testing Using Fresh Human Plasma Samples.

Area of Science:

• Clinical diagnostics
• Hemostasis and thrombosis research
• Biochemical assay validation

Background:

• Reliable measurement of factor VIII (FVIII) coagulant activity is essential for diagnosing bleeding disorders and assessing thrombotic risk.
• The complex structure and limited stability of FVIII present significant challenges in preanalytical handling and the availability of commutable control materials for hemostaseological diagnostics.

Purpose of the Study:

• To assess the commutability of frozen and lyophilized patient plasma samples for FVIII activity measurement.
• To evaluate the commutability of routinely used external quality assessment materials (EQAMs) for FVIII activity testing.

Main Methods:

• FVIII activity was measured in 97 native plasma samples using clotting and chromogenic assays from two manufacturers.
• Frozen and lyophilized aliquots of patient plasma, along with four commercially available lyophilized control materials, were analyzed.
• Commutability was assessed using Bland-Altman plots comparing candidate materials to native plasma, with a predefined criterion based on native plasma variability.

Main Results:

• Method-specific effects on FVIII activity measurement were minimal after freezing but more pronounced after lyophilization.
• Mean differences for frozen and lyophilized plasma remained within the established commutability criterion.
• All evaluated EQAMs demonstrated commutability for their intended use in external quality assessment.

Conclusions:

• Frozen and lyophilized patient plasma, as well as commercial EQAMs, are suitable for FVIII activity measurement, ensuring reliable diagnostic and monitoring capabilities.
• While commutability studies for FVIII activity are feasible, they are resource-intensive, highlighting the need for efficient validation strategies.