Factor VIII-related antigen pre-peak on crossed immunoelectrophoresis: a non-random phenomenon.

The incidence of a "pre-peak" over the well on crossed immunoelectrophoresis of factor VIII-related antigen (VIIIR:Ag) was found to be not significantly different in groups of hemophilia carriers and non-carrier women. Only 10% of hemophiliacs more than three days post-transfusion exhibited the feature. Upon transfusion 5 out of 6 hemophiliacs showed a transient appearance of the pre-peak. It was also present during pregnancy in 6 of 8 normal women, 2 hemophilia carriers and two von Willebrand's patients. The pre-peak pattern was quite reproducible both in the same sample tested on different days and in different samples from the same subject. The pre-peak material shows a line of treatment of plasma and by cryoprecipitation.