The Centers for Disease Control and Prevention (CDC), along with researchers from the Hemophilia Inhibitor Research Study (HIRS), have recently published two articles in The Journal of Thrombosis and Haemostasis. The articles describe important findings related to the formation of inhibitors (antibodies) inhibitor (antibody) in patients who have hemophilia. The study showed that people with hemophilia A and hemophilia B who develop inhibitors are likely to have a specific type of antibody (called immunoglobulin G subclass 4, or IgG4). When traditional inhibitor tests do not give clear results, tests for these antibodies may help clarify whether an inhibitor is present or even just starting to develop. You can read the scientific summary of the article here for hemophilia A and here for hemophilia B.
Main Findings from the Studies
- In people with hemophilia A or hemophilia B who have inhibitors, IgG4 antibodies to the missing or defective clotting factor were consistently found. Although other types of antibodies were sometimes also found, the presence of IgG4 antibodies appears to be the best indicator that a person has an inhibitor to the clotting factor, even when traditional inhibitor tests do not give clear results.
- IgG1 antibodies to factor VIII were found in the blood of people with hemophilia A before they developed inhibitors. This might be an early sign of future development of inhibitors.
- Taken together, the findings from these studies will help laboratories and healthcare providers identify inhibitors in patients with hemophilia A and hemophilia B when traditional testing methods fail to give clear results.