A miniaturized chemiluminescent thrombin generation assay to assess the effect of APCC in persons with hemophilia A with inhibitors: an observational study.

BACKGROUND

Monitoring of bypassing agents in persons with hemophilia A with inhibitors is complicated, especially when multiple treatment modalities are combined. The thrombin generation assay (TGA) might address these issues but is hampered by limited availability and standardization.

OBJECTIVES

To assess the performance of a novel microfluidic chemiluminescent TGA (microfluidic-TGAlum) to monitor the effect of anti-inhibitor coagulant complex (APCC) in persons with hemophilia A with inhibitors.

METHODS

The microfluidic-TGAlum was used in factor VIII (FVIII)-deficient plasma samples with different concentrations of FVIII inhibitors spiked with APCC and samples from 6 participants with hemophilia A with inhibitors before and after APCC administration. Peak height (PH), area under the curve (AUC), velocity index (VI), and lag time were compared with results obtained using the Ceveron TGA with reagent B (TGACeveron-RB).

RESULTS

Increasing concentrations of APCC spiked in FVIII-deficient plasma significantly increased PH, AUC, and VI and shortened lag time in the microfluidic-TGAlum, with strong correlation with TGACeveron-RB outcomes (r = 0.92-0.97). Microfluidic-TGAlum outcomes improved similarly after administering APCC to participants with hemophilia A with inhibitors, although thrombin generation exceeded normal values, with PH reaching 174% of that observed in normal pooled plasma. In contrast, the TGACeveron-RB displayed persistently low thrombin generation and weak correlation with microfluidic-TGAlum (r = 0.28-0.52). Exploratory follow-up experiments revealed that accumulation of prothrombin in plasma of participants with hemophilia A with inhibitors and low phospholipid concentration in the TGACeveron-RB might explain this discrepancy.

CONCLUSIONS

The microfluidic-TGAlum detects the hemostatic effects of APCC treatment in persons with hemophilia A with inhibitors. Assay-specific differences in TGA response may complicate APCC monitoring in persons with hemophilia A with inhibitors. Our findings underscore the need for further mechanistic TGA studies and standardization.