Microfluidic assay of hemophilic blood clotting: distinct deficits in platelet and fibrin deposition at low factor levels

Authors

  • T. V. COLACE,

    1. Department of Chemical and Biomolecular Engineering, Institute for Medicine and Engineering, University of Pennsylvania, Philadelphia, PA, USA
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  • P. F. Fogarty,

    1. Comprehensive Hemophilia and Thrombosis Program, Hospital of the University of Pennsylvania, Philadelphia, PA, USA
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  • K. A. Panckeri,

    1. Comprehensive Hemophilia and Thrombosis Program, Hospital of the University of Pennsylvania, Philadelphia, PA, USA
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  • R. Li,

    1. Department of Chemical and Biomolecular Engineering, Institute for Medicine and Engineering, University of Pennsylvania, Philadelphia, PA, USA
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  • S. L. Diamond

    Corresponding author
    1. Department of Chemical and Biomolecular Engineering, Institute for Medicine and Engineering, University of Pennsylvania, Philadelphia, PA, USA
    • Correspondence: Scott L. Diamond, Department of Chemical and Biomolecular Engineering, Institute for Medicine and Engineering, 1024 Vagelos Research Laboratories, University of Pennsylvania, Philadelphia, PA 19104, USA.

      Tel.: +1 215 573 5704; fax: +1 215 573 6815.

      E-mail: sld@seas.upenn.edu

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  • Manuscript handled by: P. de Moerloose
  • Final decision: F. R. Rosendaal, 16 November 2013

Summary

Background

Coagulation factor deficiencies create a range of bleeding phenotypes. Microfluidic devices offer controlled hemodynamics and defined procoagulant triggers for measurement of clotting under flow.

Objectives

We tested a flow assay of contact pathway-triggered clotting to quantify platelet and fibrin deposition distal of dysfunctional thrombin production. Microfluidic metrics were then compared with PTT or % factor activity assays.

Methods

Whole blood (WB) treated with low level corn trypsin inhibitor (4 μg mL−1) from nine healthy donors and 27 patients (deficient in factor [F] VIII, 19 patients; FIX, one patient; FXI, one patient; VWF, six patients) was perfused over fibrillar collagen at wall shear rate = 100 s−1.

Results

Using healthy WB, platelets deposited within 30 s, while fibrin appeared within 6 min. Compared with healthy controls, WB from patients displayed a 50% reduction in platelet deposition only at < 1% factor activity. In contrast, striking defects in fibrin deposition occurred for patients with < 13% factor activity (or PTT > 40 s). Full occlusion of the 60-μm high channel was completely absent over the 15-min test in patients with < 1% factor activity, while an intermediate defect was present in patients with > 1% factor.

Conclusion

Spontaneous bleeding in patients with < 1% factor activity may be linked to deficits in both platelet and fibrin deposition, a risk known to be mitigated when factor levels are raised to > 1% activity (PTT of ~40–60 s), a level that does not necessarily rescue fibrin formation under flow.

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