Multivariate Base Rates and Concussion Detection: A Comparative Study.

Recent research has yielded multivariate base rates (MBRs) of low scores in healthy populations using a widely adopted concussion screening measure, Immediate Postconcussion and Cognitive Testing (ImPACT). However, the extent to which individuals with concussion obtain reliable changes at divergent frequencies relative to healthy individuals is largely unknown. The present study examined whether MBRs of reliable change accurately discriminated between those with and without concussion. This archival review consisted of 129 healthy individuals and 81 individuals with concussion. MBRs of reliable change scores were examined at varying cutoffs and frequencies between those with and without concussion. Composites showed small to medium effect sizes in differentiating between those with and without concussion. MBRs of reliable change scores on ImPACT provided limited discriminative utility in isolation. Computations of posttest probabilities using Bayes' Theorem yielded evidence for incremental gains when utilizing MBRs of reliable change under certain constraints.