Clots formed from plasma samples with elevated prothrombin levels contain fibrin fibers with smaller mass-to-length ratios.

Platelet-rich plasma samples were collected from healthy donors and spiked with purified prothrombin to achieve prothrombin levels more than 100% of normal. Clotting was initiated by recalcifying the plasma and exposing the samples to tissue factor–bearing monocytes. Mass-to-length ratios were approximated by calculating the change in absorbance during fibrin clot formation and then normalized, such that 100% of plasma levels of prothrombin were set equal to 1. Note that the y-axis does not begin at 0. Data shown are representative of measurements on 5 separate donors.