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

• DOI: 10.1111/jth.12457
• Publication Date: 2013-11-21T14:44:48Z
• Authors: T.V. COLACE; P.F. Fogarty; K.A. Panckeri; R. Li; S.L. Diamond
• Keywords: Blood Platelets; Fibrin; 03 medical and health sciences; 0302 clinical medicine; Microfluidics; Humans; Hemophilia A; Blood Coagulation

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