Abstract
The global thrombosis test (GTT) is a point of care device that tests thrombotic and
thrombolytic status. The device exposes whole blood flow to a combination of both
high and low shear stress past and between ball bearings potentially causing thrombin
and fibrin formation. The question arises as to whether thrombosis in the GTT is dominated
by coagulation-triggered red clot or high shear-induced white clot. We investigated
the nature of the thrombus formed in the GTT, the device efficacy, human factors use,
and limitations. The GTT formed clots that were histologically fibrin-rich with trapped
red blood cells. The occlusion time (OT) was more consistent with coagulation than
high shear white clot and was strongly lengthened by heparin and citrate, two common
anticoagulants. The clot was lysed by tissue plasminogen activator (tPA), also consistent
with a fibrin-rich red clot. Changing the bead to a collagen-coated surface and eliminating
the low shear zone between the beads induced a rapid OT consistent with a platelet-rich
thrombus that was relatively resistant to heparin or tPA. The evidence points to the
GTT as occluding primarily due to fibrin-rich red clot from coagulation rather than
high shear platelet aggregation and occlusion associated with arterial thrombosis.
Keywords
GTT thrombosis - point-of-care - coagulation - SIPA - shear rate
