Global coagulation function in patients with acquired hemophilia A may be more impaired than previously anticipated, based on factor VIII (FVIII) activity assays. This is according to the results of a new study published in the International Journal of Hematology.

This impairment lasted for about 1 month after immunosuppression and treatment with FVIII-bypassing agents.

Acquired hemophilia A is thought to be caused by the spontaneous inhibition of FVIII by autoantibodies. It is different from congenital hemophilia A, where there is a mutation in the gene encoding FVIII.

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The 2 conditions also differ in clinical and laboratory features. For example, coagulation function and clinical phenotype in people with acquired hemophilia A do not always correlate with FVIII activity levels and FVIII inhibitor titers. Therefore, it is difficult to determine the effects of bypassing agents on the disease.  

“Clarification of the mechanisms underlying this pathology is required to develop more effective clinical management in this difficult coagulation disorder,” the authors of the study wrote. 

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They retrospectively analyzed the results of clot waveform analysis and thrombin and plasmin generation assays in 59 patients referred from nationwide hospitals in Japan. A clot waveform analysis is a technique based on the continuous observation of changes in light transmittance during routine clotting. This change occurs as a result of fibrin formation in plasma as blood clots.

Thrombin and plasmin generation assays provide a measure of overall coagulation and are informative in various hemorrhagic or thrombotic circumstances. The results showed that the median FVIII activity in patients with acquired hemophilia A was 3.3 IU/dL on admission. The median inhibitor titer was 63.0 BU/mL.

However, global coagulation parameters corresponded to an FVIII activity of less than 1 IU/dL. During follow-up, median FVIII activity was 1.7 IU/dL on day 0, 9.6 IU/dL on day 14, 6.7 IU/dL on day 28, 40 IU/dL on day 56, and 21.7 IU/dL on day 93.

Clot wavefront analysis-based data corresponded to an FVIII activity between 1 and 5 IU/dL until day 28. However, it reflected FVIII activity more closely after day 56. Peak plasmin was lower than 1 IU/dL until day 56 but returned to between 12 and 50 IU/dL on day 93.

Based on these findings, the authors concluded that real-time monitoring using comprehensive coagulation assays provides valuable information to evaluate hemostasis and estimate the clinical progress of acquired hemophilia A.


Takeyama M, Sasai K, Matsumoto T, et al. Comprehensive blood coagulation potential in patients with acquired hemophilia A: retrospective analyses of plasma samples obtained from nationwide centers across Japan. Int J Hematol. Published online November 1, 2021. doi:10.1007/s12185-021-03249-w