Detection of factor IX inhibitors by immunoradiometric assay
An immunoradiometric assay (IRMA) for the determination of factor IX inhibitors in haemophilia B was developed. The assay was based on competitive binding between radiolabelled anti-IX and inhibitors in the test material of immobilized IX:C. 5 haemophiliacs with known inhibitors were investigated with the new method and with a conventional neutralization test. An inhibitor titre as low as 5 X 10(-