Factor VIII Procoagulant Antigen Recovery Is a Dose-Related Response to Factor VIII Concentrate Infusions

Abstract

The recovery and initial half-disappearance rate of factor VIII procoagulant activity (VIIIC) and procoagulant antigen (VIIICAg) were studied in 9 haemophilia A patients following infusion of factor VIII concentrates to varying plasma VIIIC levels. While VIIIC recovery was independent of dose, the VIIICAg recovery varied in a dose-dependent fashion. The excess of VIIICAg relative to VIIIC found in the factor VIII concentrates (VIIICAg/VIIIC ratios of 1.9–3.1) was not observed in plasma samples taken after low level infusions (plasma VIIIC < 1 U/ml) but a significant excess of VIIICAg was observed in higher level infusions. The VIIICAg recovery of post-infusion plasma was not increased by treatment with phospholipase C.

Measurement of Factor VIII Procoagulant Antigen in Normal Subjects and in Hemophilia A Patients by an Immunoradiometric Assay and by an Enzyme-Linked Immunosorbent Assay

“…These findings correspond to the ob servation of other authors, who generally found FVIILAg/FVIILC ratios greater than 1.0 [18][19][20], There are presently 4 studies that have concerned themselves with the assessment of FVIILAg recoveries after infusion of FVIII in a small number of hemophilia A patients [18][19][20][21]. In all cases, the FVIILAg recoveries were significantly lower than those of FVIILC when administered in dosages that lead to an FVIILC increase of less than 1 U/ml.…”

“…Similar observations were made by Holmberg et al [18] and Taylor et al [20] who also deter mined FVIILAg with solid-phase assays. In contrast.…”

“…In all cases, the FVIILAg recoveries were significantly lower than those of FVIILC when administered in dosages that lead to an FVIILC increase of less than 1 U/ml. The recoveries were approximately equal with higher dosages of FVIII [20],…”