Concussion Biomarkers Assessed in Collegiate Student-Athletes (BASICS) I: Normative study.

Abstract

To describe variability in concussion biomarker concentrations collected from serum in a sample of healthy collegiate athletes, as well as report reliability metrics in a subsample of female athletes. In this observational cohort study, β-amyloid peptide 42 (Aβ₄₂), total tau, S100 calcium binding protein B (S100B), ubiquitin carboxy-terminal hydrolyzing enzyme L1 (UCH-L1), glial fibrillary acidic protein, microtubule associated protein 2, and 2',3'-cyclic-nucleotide 3'-phosphodiesterase (CNPase) serum concentrations were measured in 415 (61% male, 40% white, aged 19.0 ± 1.2 years) nonconcussed collegiate athletes without recent exposure to head impacts. Standardized normative distributions are reported for each biomarker. We evaluated main effects (analyses of variance) of sex and race, reporting demographic-specific normative metrics when appropriate. In a subset of 31 female participants, test-retest reliability (Pearson <i>r</i>) and reliable change indices (80%, 90%, and 95% confidence intervals) across a 6- to 12-month interval are reported for Aβ₄₂, total tau, S100B, and UCH-L1. Males exhibited higher UCH-L1 (<i>p</i> < 0.001, Cohen <i>d</i> = 0.75) and S100B (<i>p</i> < 0.001, <i>d</i> = 0.56) than females, while females had higher CNPase (<i>p</i> < 0.001, <i>d</i> = 0.43). Regarding race, black participants had higher baseline levels of UCH-L1 (<i>p</i> < 0.001, <i>d</i> = 0.61) and S100B (<i>p</i> < 0.001, <i>d</i> = 1.1) than white participants. Conversely, white participants had higher baseline levels of Aβ₄₂ (<i>p</i> = 0.005, <i>d</i> = 0.28) and CNPase (<i>p</i> < 0.001, <i>d</i> = 0.46). Test-retest reliability was generally poor, ranging from -0.02 to 0.40, and Aβ₄₂ significantly increased from time 1 to time 2. Healthy collegiate athletes express concussion-related serum biomarkers in variable concentrations. Accounting for demographic factors such as sex and race is essential. Evidence suggested poor reliability for serum biomarkers; however, understanding how other factors influence biomarker expression, as well as knowledge of reliable change metrics, may improve clinical interpretation and future study designs.