Assay discrepancies using human coagulation factor VIII chromogenic kits: Results from a plasma-derived factor VIII...

Area of Science:

• Biotechnology and Pharmaceutical Analysis
• Hematology and Coagulation Diagnostics

Background:

• Discrepancies in chromogenic assays for Factor VIII (FVIII) products were reported by European laboratories.
• These variations impact the accurate potency determination of FVIII therapeutic concentrates.

Purpose of the Study:

• To investigate and identify the causes of FVIII chromogenic assay discrepancies.
• To compare the performance of different chromogenic kits (Coatest®, Coamatic®, Siemens) under controlled conditions.

Main Methods:

• A collaborative study involving multiple laboratories assessing FVIII products.
• Measurement of observed Factor X (FX) activation times (T1/2) for each kit.
• Comparison of observed T1/2 with manufacturer-prescribed T1/2 for potency calculations.

Main Results:

• Significant potency discrepancies were found between Coatest®/Coamatic® and Siemens/Coamatic® kits when using prescribed incubation times.
• Coamatic® kits generally yielded higher potencies.
• Observed T1/2 values varied significantly between laboratories and did not match prescribed times, impacting potency results.

Conclusions:

• Chromogenic FVIII potency assays can exhibit significant inter-kit and inter-laboratory variability.
• Using actual observed T1/2 incubation times, rather than prescribed ones, can reduce potency discrepancies.
• Laboratories should determine kit-specific FX activation curves to establish optimal T1/2 for accurate FVIII potency determination.