PRENATAL-DIAGNOSIS OF HEMOPHILIA-B BY AN IMMUNORADIOMETRIC ASSAY OF FACTOR-IX

  • 1 January 1980
    • journal article
    • research article
    • Vol. 56  (3) , 397-401
Abstract
An immunoradiometric assay of factor IX was developed based on homologous antibodies that arose in a hemophilic patient. With this assay, 11 of 12 patients with severe hemophilia B had factor IX antigen levels below 1 U/dl and 6 patients with mild hemophilia B had various levels. Factor IX antigen in 8 fetuses (16th-20th gestational week) aborted for therapeutic reasons ranged from 1.8 to 10.0 U/dl. Amniotic fluids (6) contained 0.28-1.2 U/dl factor IX antigen. Using the immunoradiometric assay, hemophilia B was diagnosed prenatally in 1 fetus at risk. No factor IX antigen (< 0.2 U/dl) was detectable in the fetoscopic sample. After termination of the pregnancy, analysis of blood from the abortus confirmed the diagnosis of severe hemophilia B. Very sensitive immunologic assays, such as the one described here, will prove useful in prenatal diagnosis of severe hemophilia B, since determination of factor IX activity in fetoscopic samples is unreliable because of possible contamination with thromboplastic material.