ABSTRACT Unexplained heterogeneity in outcomes following traumatic brain injury (TBI) precludes accurate prognostication and is cited as a critical barrier that partially accounts for decades of failed trials of neuroprotective therapies. To address this critical barrier, several international research consortia were established to better understand factors influencing recovery from pediatric and adult TBI. These efforts are strengthened by the adoption of common data elements (CDEs), the “gold standard” of psychometrically validated measures of outcomes and their predictors. One factor that may account for unexplained heterogeneity in outcomes is rehabilitation utilization; however, it is not well studied because no scientifically rigorous, comprehensive, standardized, or validated measure of rehabilitation utilization currently exists. TBI rehabilitation encompasses a wide range of multidisciplinary services spanning the care continuum from the ICU to the community. Utilization of rehabilitation services following pediatric TBI is highly variable. Our long- term goal is to examine whether variance in rehabilitation utilization accounts for some of the unexplained heterogeneity in outcomes following pediatric TBI. If we can reduce heterogeneity in our models of TBI recovery, we can provide more accurate prognostication and improve our ability to test the efficacy of treatments. As a critical first step, we will develop, refine, and conduct initial validation of a caregiver-report measure of rehabilitation utilization, the Rehabilitation Utilization Measure (RUM). We will combine qualitative and quantitative methods to engage caregiver, clinician, and scientist stakeholders in measure development and refinement and to conduct initial measure validation. This proposal addresses NCMRR research priorities: (1) understanding real-world health service access; (2) developing objective measures that may predict rehabilitation treatment response; and (3) identifying, preventing, and treating key secondary conditions, including cognitive impairment. Successful completion will result in an innovative, rigorous, initially validated and refined caregiver-report measure of rehabilitation utilization that can be further validated and adapted for research and clinical use in children or adults from wide-ranging rehabilitation populations and considered for inclusion as a CDE in future TBI studies. The PIs will use this R03 data in direct support of an R01 with aims to: (1) develop an mHealth version of the RUM; (2) examine accuracy and added value of caregiver reporting of rehabilitation utilization relative to insurance claims data; and (3) examine associations of rehabilitation utilization as reported on the RUM with its environmental (e.g. rehabilitation availability) and patient characteristic (e.g. TBI severity, functional status, psychosocial adversity, healthcare access ) determinants, and with neurobehavioral outcomes. The potential impact of this resea...