Detection of genetic variants of haemophilia B with an immunosorbent technique.

Abstract

Summary. With an immunosorbent technique, we have found multiple genetic variants of haemophilia B. In one variant there is no detectable material that cross‐reacts with a human anti‐factor‐IX antibody. This variant is defined as negative for cross‐reacting material (CRM−). There is also a CRM+ variant in which the factor‐IX deficient plasma has the capacity to neutralize as much antibody as does normal plasma. There is an intermediate variety that neutralizes the specific antibody to a degree which is proportional to the factor‐IX clotting activity. This last group has been designated as having reduced cross‐reacting material (CRMR). The CRMR group is probably heterogeneous, and it is likely that many genetic variants of haemophilia B exist.