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Serologic evidence that factor IX inhibitor in the plasma of hemophilia B patients detects factor IX on normal red cells
Author(s) -
Swanson J. L.,
Moertel C. L.,
Stroncek D. F.,
Key N. S.
Publication year - 1996
Publication title -
transfusion
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.045
H-Index - 132
eISSN - 1537-2995
pISSN - 0041-1132
DOI - 10.1046/j.1537-2995.1996.36596282593.x
Subject(s) - factor ix , antibody , polyclonal antibodies , titer , red cell , haemophilia b , chemistry , microbiology and biotechnology , medicine , red blood cell , serology , immunology , biochemistry , biology , haemophilia , haemophilia a , pediatrics
BACKGROUND: Patients with hemophilia B lack factor IX (F IX). These patients may become alloimmunized after the transfusion of F IX concentrates and may develop F IX inhibitors, which have been characterized as polyclonal IgG4 alloantibodies. Two cases in which F IX inhibitors caused difficulty in compatibility testing and antibody identification were encountered. It was hypothesized that, because F IX is present in normal plasma, it might be adsorbed by red cells in vivo and then be detected during antibody screening tests with serum containing F IX inhibitors. CASE REPORT: Sera from two African American half‐brothers with hemophilia B were incompatible with all common and rare red cell phenotypes tested in the anti‐human globulin test, but did not react with each other's red cells. The brothers' red cell antibodies were neutralized with both normal plasma and a commercially available F IX concentrate, which indicated that the red cell incompatibility was most probably caused by their F IX inhibitors. Red cells from an unrelated patient with hemophilia B and a very low titer of F IX inhibitor were tested against the half‐brothers' sera and did not react. The compatible red cells from one of the half‐brothers and the unrelated patient with hemophilia B adsorbed F IX from normal plasma or F IX concentrate after 37 degrees C incubation; this rendered them incompatible with the plasma containing F IX inhibitor from the other half‐brother. CONCLUSION: F IX appears to be present on normal red cells and may be detected during compatibility and antibody identification procedures when serum or plasma containing F IX inhibitors is tested.