Factor IX in warfarin treated patients.

Abstract

Abstract The presence of inactive factor IX molecules (acarboxy-IX) was demonstrated in plasma from warfarin treated patients by immunoelectrophoretic techniques using a precipitating rabbit antiserum against human factor IX. The level of factor IX activity (mean 0.42 units/ml) was lower than the level of factor IX antigen determined by an electroimmunoassay technique (mean 0.70 units/ml) in 34 of the 35 patients studied. The percentage Thrombotest values correlated positively with the level of factor IX activity (r=0.74) and negatively with the relative amount of acarboxy-IX (r=−0.54). Crossed immunoelectrophoresis in the presence of calcium ions of patient plasma revealed a factor IX antigen with a faster electrophoretic mobility than that of normal factor IX. Factor IX antigen from the patient with the largest amount of acarboxy-IX had a lower affinity to BaSO 4 than factor IX antigen from normal plasma. Neutralization of factor IX in the patient plasma samples by antiserum gave increased percentage Thrombotest values but had no effect on the Normotest values. The effect of the antiserum on the Thrombotest values was about the same on the patient plasma samples as on undiluted and diluted plasma from normal persons.