High agreement between one-stage clot-based and chromogenic factor VIII activity assays

Area of Science:

• Hematology
• Clinical Chemistry
• Biotechnology

Background:

• Gene therapy studies report discrepancies between one-stage and chromogenic factor VIII (FVIII) assays.
• Previous comparative studies of these assays are limited by small sample sizes.
• Accurate FVIII activity measurement is crucial for managing bleeding disorders.

Purpose of the Study:

• To compare the performance of the one-stage clot-based assay and the chromogenic assay in measuring FVIII activity.
• To evaluate the agreement between these two common FVIII assays in a large patient cohort.
• To identify factors influencing potential discrepancies between the assays.

Main Methods:

• A retrospective study analyzed 3623 blood samples from various hematologic conditions.
• Both one-stage clot-based and chromogenic assays were performed for FVIII measurements.
• Bland-Altman analysis was used to assess agreement and identify bias between the assays.

Main Results:

• The mean FVIII activity was comparable between the one-stage (1.2 IU/ml) and chromogenic (1.2 IU/ml) assays.
• Bland-Altman analysis revealed excellent agreement with minimal bias (-0.0034).
• High baseline FVIII activity and specific diagnoses predicted assay disagreement (P < 0.001); however, low FVIII activity (<0.4 IU/ml) showed significant discrepancies (21.1%), with overestimation by the one-stage assay.

Conclusions:

• The one-stage clot-based and chromogenic FVIII assays demonstrate excellent agreement for routine FVIII activity measurement.
• While generally concordant, specific clinical conditions and FVIII activity levels may lead to discrepancies.
• Further investigation into the causes of disagreement in specific subgroups is warranted.