Prenatal diagnosis of hemophilia B by an immunoradiometric assay of factor IX

Lars Holmberg, B Gustavii, E Cordesius, A C Kristoffersson, R Ljung, L Löfberg, P Strömberg, Inga Marie Nilsson

Research output: Contribution to journalArticlepeer-review


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. Six amniotic fluids contained 0.28-1.2 U/dl factor IX antigen. Using the immunoradiometric assay, we could diagnose hemophilia B prenatally in one 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. We conclude that 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 unrealiable because of possible contamination with thromboplastic material.

Original languageEnglish
Pages (from-to)397-401
Number of pages5
Issue number3
Publication statusPublished - 1980 Sept

Subject classification (UKÄ)

  • Hematology

Free keywords

  • Dose-Response Relationship, Immunologic
  • Factor IX
  • Female
  • Hemophilia B
  • Humans
  • Male
  • Pregnancy
  • Prenatal Diagnosis
  • Radioimmunoassay
  • Case Reports
  • Journal Article


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