Recombinant Factor VIIA in the Treatment of Bleeding

Madhu V. Midathada, MD; Paulette Mehta, MD; Milton Waner, MD; Louis M. Fink, MD

Disclosures

Am J Clin Pathol. 2004;121(1) 

In This Article

Monitoring of rFVIIa

Laboratory monitoring of hemostatic efficacy in patients treated with rFVIIa is complex. Standard PT and aPTT have limitations and do not correlate with the clinical picture. Factor VII activity assays were used in the past to monitor rFVIIa activity. A modified version of the Staclot VIIa-rTF assay (Diagnostica Stago, Asnieres, France) has been developed that is suitable for monitoring treatment with rFVIIa at low concentrations.[131]

A thromboelastogram is done on an automated instrument that demonstrates changes occurring during blood coagulation and fibrinolysis. Thromboelastography was evaluated to be better than aPTT as a monitor of hemostatic effects when using rFVIIa.[132] Whole blood elasticity as measured by thromboelastography has been shown to improve following rFVIIa therapy. In vivo and ex vivo rotating thromboelastography measurements showed that rFVIIa shortened whole blood clotting time, although normalization did not occur. The efficacy of these principles needs to be tested further.[129]

A study comparing factor VII activity and rFVIIa assays for 24 patients who received rFVIIa treatment showed a good correlation (r = 0.91), but the values for factor VII activity were 1.63 times higher than those for the rFVIIa method and a relatively wide margin in the interval of the factor VII/rFVIIa ratio was obtained. Cid et al[133] believe that the rFVIIa assay would be more suitable for the monitoring of rFVIIa treatment because the factor VII assay has wide interlaboratory variability.

The effect of rFVIIa on the PT was compared with the effect of a standard volume of FFP in preterm neonates with prolonged PTs. The PT remained lower in the rFVIIa group (P = .01) at 3 hours than in the FFP group; the differences at 6 and 12 hours were statistically insignificant.[134]

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