More than 75% of patients presenting to level I trauma centers in the United States with suspicion of TBI sufficient to require a clinical computed tomography scan report injury-related symptoms 3 months later. There are currently no approved treatments, and few clinical trials have evaluated possible treatments. Efficient trials will require subject inclusion and exclusion criteria that balance cost-effective recruitment with enrolling individuals with a higher chance of benefiting from the interventions. Using data from the Transforming Research and Clinical Knowledge in Traumatic Brain Injury (TRACK-TBI) study, we examined the relationship of 3-month symptoms to pre-injury, demographic, and acute characteristics as well as 2-week symptoms and blood-based biomarkers to identify and evaluate factors that may be used for sample enrichment for clinical trials. Many of the risk factors for TBI symptoms reported in the literature were supported, but the effect sizes of each were small or moderate (< 0.5). The only factors with large effect sizes when predicting 3-month symptom burden were TBI-related (i.e., post-concussive) and post-traumatic stress symptom levels at 2 weeks (respective effect sizes 1.13 and 1.34). TBI severity was not significantly associated with 3-month symptom burden (p = 0.37). Using simulated data to evaluate the effect of enrichment, we showed that including only people with high symptom burden at 2 weeks would permit trials to reduce the sample size by half, with minimal increase in screening, as compared with enrolling an unenriched sample. Clinical trials aimed at reducing symptoms after TBI can be efficiently conducted by enriching the included sample with people reporting a high early symptom burden.

Symptom endorsement after traumatic brain injury (TBI) is common acutely post-injury and is associated with other adverse outcomes. Prevalence of persistent symptoms has been debated, especially in mild TBI (mTBI). A cohort of participants ≥17 years with TBI (n = 2039), 257 orthopedic trauma controls (OTCs), and 300 friend controls (FCs) were enrolled in the TRACK-TBI study and evaluated at 2 weeks and 3, 6, and 12 months post-injury using the Rivermead Post-Concussion Symptoms Questionnaire (RPQ). TBI participants had significantly higher symptom burden than OTCs or FCs at all times, with average scores more than double. TBI cases showed significant decreases in RPQ score between each evaluation (p < 0.001), decreasing ∼1.7 points per month between 2 weeks and 3 months and 0.2 points per month after that. More than 50% of the TBI sample, including >50% of each of the mild and moderate/severe TBI subsamples, continued to endorse three or more symptoms as worse than pre-injury through 12 months post-injury. A majority of TBI participants who endorsed a symptom at 3 months or later did so at the next evaluation as well. Contrary to reviews that report symptom resolution by 3 months post-injury among those with mTBI, this study of participants treated at level 1 trauma centers and having a computed tomography ordered found that persistent symptoms are common to at least a year after TBI. Additionally, although symptom endorsement was not specific to TBI given that they were also reported by OTC and FC participants, TBI participants endorsed over twice the symptom burden compared with the other groups.