Fibers in fibrin clots formed in the presence of elevated prothrombin are thinner than fibers formed in the presence of normal prothrombin levels.

Fibrin fibers in transmission electron micrographs of fibrin gel networks from clots formed in the presence of 100% and 300% plasma prothrombin levels were measured as described in “Materials and methods.” Three separate donors are depicted (1, 2, and 3). Differences in the mean thickness of fibrin fibers (horizontal lines for each data set) formed in the presence of 100% prothrombin illustrate the platelet donor-dependent differences observed in the assays.32 33 However, clots formed in the presence of 300% prothrombin were consistently composed of thinner fibers than clots formed in the presence of normal prothrombin levels (P < .0215).