Thrombosis Research
Volume 126, Issue 2 , Pages 119-123, August 2010

The “normal” factor VIII concentration in plasma☆

  • Saulius Butenas

      Affiliations

    • Department of Biochemistry, College of Medicine, University of Vermont, Burlington, VT, USA
    • Corresponding Author InformationCorresponding author. University of Vermont, 208 South Park Drive, Room 235A, Colchester, VT 05446, USA. Tel.: +1 802 656 0350; fax: +1 802 656 2256.
    • ,
  • Behnaz Parhami-Seren

      Affiliations

    • Department of Biochemistry, College of Medicine, University of Vermont, Burlington, VT, USA
    • Present address: Moorpark College, Moorpark, CA.
    • ,
  • Anetta Undas

      Affiliations

    • Institute of Cardiology, Jagiellonian University, Krakow, Poland
    • ,
  • David N. Fass

      Affiliations

    • Mayo Medical School, Rochester, MN, USA
    • ,
  • Kenneth G. Mann

      Affiliations

    • Department of Biochemistry, College of Medicine, University of Vermont, Burlington, VT, USA

Received 2 February 2010; received in revised form 12 March 2010; accepted 7 April 2010. published online 10 May 2010.

Abstract 

Introduction

The quantitation of factor (F)VIII by activity-based assays is influenced by the method, procedure, the quality and properties of reagents used and concentrations of other plasma proteins, including von Willebrand factor (VWF).

Objective

To compare FVIII concentrations measured by activity-based assays with those obtained by an immunoassay and to establish the influence of plasma dilution on the FVIII clotting activity (FVIIIc).

Methods

The APTT, a chromogenic assay (Coatest) and two in-house immunoassays were used. Albumin-free recombinant FVIII was used as the calibrator in all assays.

Results

For a group of 44 healthy individuals (HI), the mean value observed for FVIII antigen (FVIIIag; 1.22±0.56nM; S.D.) is substantially higher than that for FVIIIc (0.65±0.29nM) and the chromogenic assay (FVIIIch; 0.50±0.23nM). A positive correlation between FVIIIag and VWFag with R2=0.20 was observed. Since plasma VWF has an inhibitory effect on FVIIIc, we evaluated the influence of plasma dilutions on FVIIIc in HI (n=105). At a 4-fold dilution, estimates of FVIIIc by clotting assay were much lower than FVIIIag (0.77±0.31 vs. 1.14±0.48nM). At 10- and 25-fold dilutions, the estimated FVIIIc increased to 0.87±0.36 and 0.94±0.44nM, respectively.

Conclusions

1) In plasma, FVIIIag is higher than FVIIIc and FVIIIch; and 2) Real FVIII concentrations in plasma can be estimated by measuring FVIIIag.

Keywords: Factor VIII antigen, Factor VIII activity, von Willebrand factor, APTT assay, Coatest assay, Immunoassays

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☆ Portions of this work were presented at the XXII Congress of the International Society on Thrombosis and Haemostasis, Boston, MA, USA, July 16, 2009 (Abstract PP-TH-154).

PII: S0049-3848(10)00229-X

doi:10.1016/j.thromres.2010.04.004

Thrombosis Research
Volume 126, Issue 2 , Pages 119-123, August 2010

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