What are factor inhibitors?

Updated: Feb 07, 2020
  • Author: Bishnu Prasad Devkota, MD, MHI, FRCS(Edin), FRCS(Glasg), FACP; Chief Editor: Eric B Staros, MD  more...
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An inhibitor exists for nearly every procoagulant, with the inhibitor to factor VIII being the most common. Detection of factor VIII inhibitor is accomplished by mixing the test plasma with a known amount of factor VIII. Following a 2-hour incubation period at 37°C, a factor VIII assay is used to determine residual factor VIII activity. The presence or absence of a factor VIII inhibitor can be determined through comparison of the difference in factor VIII activity between the incubation mixture and a control mixture. The partial thromboplastin time (PTT) is prolonged by some antibodies only after incubation. [1]

Among the many protease inhibitors in plasma, tissue factor pathway inhibitor (TFPI) and antithrombin are the ones that are most specifically involved in inhibition of coagulation factors. Another potentially important regulator of the coagulation system, the protein Z/protein Z–dependent protease inhibitor (ZPI) system, is also emerging. [2]

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