Thrombin generation in haemophilia A patients with mutations causing factor VIII assay discrepancy

Area of Science:

• Hematology
• Coagulation Science
• Clinical Diagnostics

Background:

• Mild hemophilia A patients often exhibit discrepancies between factor VIII (FVIII) measurements from one-stage clotting assays (FVIII:C) and two-stage chromogenic assays (FVIII:C(CH)).
• The clinical significance of this assay discrepancy and which assay better represents coagulation potential remains unclear.

Purpose of the Study:

• To assess the global coagulant ability in hemophilia A patients with FVIII assay discrepancy using calibrated automated thrombography (CAT).
• To determine which FVIII assay correlates better with thrombin generation parameters in patients with assay discrepancies.

Main Methods:

• Investigated 18 patients with FVIII assay discrepancy (Arg531His/Cys or Arg698Trp mutations), 12 with concordant FVIII values, and 15 healthy controls.
• Measured FVIII levels using both one-stage clotting and two-stage chromogenic assays.
• Assessed thrombin generation in platelet-poor plasma using CAT with low tissue factor (1 pm).

Main Results:

• FVIII:C(CH) values were lower than FVIII:C in the discrepant group (1.5- to 8-fold).
• All hemophilia patients showed affected CAT parameters; endogenous thrombin potential (ETP) was reduced (58-67% of normal), and peak thrombin was significantly reduced (27-30% of normal) in both discrepant and concordant groups.
• The FVIII:C assay showed the strongest correlation with ETP (r²=0.44) and peak thrombin (r²=0.27) in the discrepant group.

Conclusions:

• Calibrated automated thrombography reveals impaired thrombin generation in hemophilia A patients, irrespective of FVIII assay discrepancy.
• The one-stage FVIII:C assay appears to better reflect the global coagulant ability and thrombin generation potential compared to the FVIII:C(CH) assay in patients with mild hemophilia A and assay discrepancies.