Interpreting Change in Sport Concussion Assessment Tool-5th Edition (SCAT5) Scores in National Rugby League Women’s Premiership Players

The Sport Concussion Assessment Tool (SCAT) is a multimodal, evidence-based tool designed for repeat administration at baseline, pre-season and/ or for post-injury assessments, following a sport related concussion. Repeat administration of concussion assessment tools requires clinicians to understand the instrument's stability and test-retest reliability. Typically, clinicians compare post-injury scores with baseline test results in order to determine whether a clinically significant change has occurred. The National Rugby League Women's (NRLW) Premiership was created in 2018, with a concussion management process requiring annual pre-season baseline medical assessments of players using the Sport Concussion Assessment Concussion Tool-5th Edition (SCAT5). Although baseline normative data have been published for the SCAT5, reliability data are limited in women. The purpose of this study was to examine the one-year test-retest reliability of the SCAT5 component scores, and to develop reliable change indices, for the women's league. Participants were 63 NRLW players (mean age = 26.9 years, SD = 5.5) from the 2018-2019 and 2019-2020 seasons. Team medical staff conducted the baseline SCAT5 assessments each year. Test-retest reliability estimates for each of the SCAT5 components were low to moderate (ICCs = 0.28-0.57). The following change scores, reflecting worsening, occurred in 20% or fewer of the sample: +3 symptom number, + 4 symptom severity, and - 2 on the Standardized Assessment of Concussion total score. A change of + 2 total modified Balance Error Scoring System errors occurred in fewer than 10% of the NRLW players between the test and retest. SCAT5 scores had low to moderate test-retest reliability across a one-year period. Reliable change scores for the SCAT5 were developed in this study for use with professional women rugby league players. When evaluating post-injury SCAT5 scores, it can be helpful to consider both what the score means compared to normative reference values and compared to the athlete's individual baseline scores.