Moreover, mechanisms of tau release into circulation remain unclear.<h4>Objective</h4>To evaluate concentrations of phosphorylated and nonphosphorylated tau variants in the blood of patients with multiple traumatic injuries on days 0, 1, 5, and 10 and investigate biological processes driving tau release.<h4>Design, setting, and participants</h4>This multiple-trauma cohort (injury severity score, ≥18) included 45 severely injured patients with (n = 27) and without (n = 18) moderate-to-severe traumatic brain injury on emergency computed tomographic imaging. The gene discussed is MAPT; the disease is brain injury.