Factor Structure and Measurement Invariance Across Sex of the Sport Concussion Assessment Tool Symptom Inventory.

Objective: Describe the factor structure of the 22-symptom Sport Concussion Assessment Tool (SCAT), using confirmatory factor analysis (CFA) for a priori hypothesized symptom domains.

Study design: Prospective observational study.

Setting/participants: Collegiate student-athletes with concussion.

Independent variables: Symptoms were collected via the SCAT symptom checklist.

Outcome measures: We created symptom domains based on previous literature, guided by clinical expertise. To determine which symptom grouping best represent the data, we used CFA and compared a single-domain model to 3- and 6-domains. We examined fit statistics to assess relative and absolute model fit. Motivated by differences in the prevalence of some individual symptoms by sex in our study, we also examined model invariance by sex to determine if symptoms were being measured as part of the same underlying construct(s).

Results: Among 1160 concussions (male, n = 667; female, n = 493) between 2015 and 2020, all 3 symptom structures seemed to fit the data well, with 3- and 6-domains fitting better than 1-domain. The 6-domain structure fit the data best with the following domains: headache, vestibulo-ocular, sensory, cognitive, sleep, and affective. All 3 structures showed configural and metric invariance by sex.

Conclusions: We demonstrate that the SCAT symptom structure is best represented through 6 specific factors; however, the 3-factor model also demonstrated good fit. Key differences between the 3- and 6-domain models may make 1 model more appropriate than the other depending on the research question being addressed. Symptom structures were configurally and metrically invariant by sex, meaning that symptom measures represent symptom domain factors in the same way across sex.