Evaluation of thromboelastography for monitoring recombinant activated factor VII ex vivo in haemophilia A and B patients with inhibitors: a multicentre trial.
Predicting the clinical effect of bypassing agents such as recombinant activated factor VII in haemophilia patients with inhibitors is hampered by the limited availability of reliable laboratory monitoring tools. This multicentre, open-label trial aimed to explore the dose-response relationship between recombinant activated factor VII concentration and thromboelastography parameters in blood samples from patients with haemophilia A or B with inhibitors in a nonbleeding state. Citrated whole blood samples from 16 patients (>or=16 years) with haemophilia A or B were spiked ex vivo with recombinant activated factor VII (1.2, 1.6, 2.0, 2.6, 3.0, 3.5 microg/ml), corresponding approximately to doses of 90-270 microg/kg. Samples were analysed by Thromboelastograph or Rotation Thromboelastography (three United States and three European centres, respectively) within 30 min (final lipidated recombinant tissue factor 1: 17 000; final CaCl2 15 mM). Thromboelastograph/Rotation Thromboelastography parameters showed large intersubject variation in the baseline profiles. There was a clear effect when recombinant activated factor VII was added; however, a clear concentration-response relationship was only detected for one patient. This is likely due to the fact that the curves were not sufficiently abnormal that led to reduced assay sensitivity. Our preliminary results suggest that thromboelastography may potentially be a clinically useful tool for monitoring changing concentrations of recombinant activated factor VII in haemophilia patients, but only when the baseline curve is significantly abnormal. Thus, test conditions may need to be optimized before Thromboelastograph/Rotation Thromboelastography can be utilized for all inhibitor patients.
Young
Guy
G
Children's Hospital Los Angeles, Los Angeles, California 90027, USA. gyoung@chla.usc.edu
Ebbesen
Liselotte S
LS
Viuff
Dorthe
D
Di Paola
Jorge
J
Konkle
Barbara A
BA
Negrier
Claude
C
Pasi
John
J
Ingerslev
Jørgen
J
D000328:Adult; D000368:Aged; D001777:Blood Coagulation / Q000187:drug effects; D001779:Blood Coagulation Factors / Q000008:administration & dosage*; D004305:Dose-Response Relationship, Drug; D015942:Factor VIIa / Q000008:administration & dosage*; D006467:Hemophilia A / Q000097:blood / Q000188:drug therapy*; D002836:Hemophilia B / Q000097:blood / Q000188:drug therapy*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011994:Recombinant Proteins / Q000008:administration & dosage; D013916:Thrombelastography
D001779:Blood Coagulation Factors; D011994:Recombinant Proteins; C103587:recombinant FVIIa; D015942:Factor VIIa