The Sport Concussion Assessment Tool: A Systematic Review

Aaron M. Yengo-Kahn, BS; Andrew T. Hale, BS; Brian H. Zalneraitis, BS; Scott L. Zuckerman, MD; Allen K. Sills, MD; Gary S. Solomon, PhD


Neurosurg Focus. 2016;40(4):e6 

In This Article

Abstract and Introduction


Objective Over the last 2 decades, sport-related concussion (SRC) has garnered significant attention. Even with increased awareness and athlete education, sideline recognition and real-time diagnosis remain crucial. The need for an objective and standardized assessment of concussion led to the eventual development of the Sport Concussion Assessment Tool (SCAT) during the Second International Conference on Concussion in Sport in 2004, which is now in its third iteration (SCAT3). In an effort to update our understanding of the most well-known sideline concussion assessment, the authors conducted a systematic review of the SCAT and the evidence supporting its use to date.

Methods English-language titles and abstracts published between 1995 and October 2015 were searched systematically across 4 electronic databases and a review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines adapted for the review of a heterogeneous collection of study designs. Peer-reviewed journal articles were included if they reported quantitative data on any iteration of the SCAT, Standardized Assessment of Concussion (SAC), or modified Balance Error Scoring System (mBESS) data at baseline or following concussion in an exclusively athlete population with any portion older than 13 years of age. Studies that included nonathletes, only children less than 13 years old, exclusively BESS data, exclusively symptom scale data, or a non–SCAT-related assessment were excluded.

Results The database search process yielded 549 abstracts, and 105 full-text articles were reviewed with 36 meeting criteria for inclusion. Nineteen studies were associated with the SAC, 1 was associated with the mBESS exclusively, and 16 studies were associated with a full iteration of the SCAT. The majority of these studies (56%) were prospective cohort studies. Male football players were the most common athletes studied. An analysis of the studies focused on baseline differences associated with age, sex, concussion history, and the ability to detect an SRC.

Conclusions Looking toward the upcoming Concussion in Sport Group meeting in fall 2016, one may expect further revision to the SCAT3. However, based on this systematic review, the authors propose further, in-depth study of an already comprehensive concussion test, with acute, diagnostic, as well as long-term use.


Over the last 2 decades, sport-related concussion (SRC) has emerged as a major public health problem with many stakeholders.[4,42,56] The Centers for Disease Control and Prevention estimate up to 3.8 million instances of SRC in any given year.[17,27] Even with increased awareness and attempts at athlete education,[7,26] sideline recognition and real-time diagnosis by team physician or training staff remains crucial.[17,36,39]

Recognition and diagnosis of SRC based on symptoms alone may be challenging given the variability in symptom reporting.[40] Due to the subjective nature of symptom endorsement, athletes may fail to disclose or purposefully hide symptoms from sideline staff to remain in the game.[20,25] The need for an objective and standardized assessment of concussion, including brief screening of neurocognitive and neurological functions in addition to symptom assessment, led to the development of the Standardized Assessment of Concussion (SAC) in 1997.[31–33] During the Second International Conference on Concussion in Sport in 2004, the SAC was combined with a standardized symptom scale (the Post-Concussion Symptom Scale [PCSS]), sport-specific orientation questions (i.e., modified Maddocks' questions), on-field markers of concussion (e.g., amnesia, loss of consciousness), and guidelines for a systematic, stepwise return to play to create the first iteration of the Sport Concussion Assessment Tool (SCAT).[34] While the primary purpose of the SCAT was to standardize sideline diagnosis of concussion, it also served as a tool for patient education.[34]

At the third meeting of the Concussion in Sport Group,[35] the SCAT underwent revisions to include the additions of:1) the Glasgow Coma Scale (GCS); 2) alternate word lists for the immediate and delayed recall portion of the SAC; and 3) a modified version of the Balance Error Scoring System (mBESS, consisting of 3 stances performed on a hard surface).[35] Although the SCAT2 was more labor intensive and required greater time to administer, it was designed for both sideline and serial use to track an athlete's recovery during subsequent clinical assessments.[21,35] In the most recent revision (SCAT3), published in 2013,[14] additional physical/objective signs (i.e., blank/vacant look, cervical stability assessment) were added with the option of using either foam stances or a timed tandem gait task for postural stability assessment. The SAC and PCSS remained unchanged in the SCAT3 from its original iteration.[14] In addition, a SCAT3 version tailored to children (age < 13 years) was introduced, the Child-SCAT3.[36]

Prior to the release of the SCAT3, the SCAT2 became widely used by certified athletic trainers and team physicians.[21,39] Administration of the SCAT2 had been made more efficient with the advent of smartphone and tablet versions.[5] Because few generalizable studies have been conducted to empirically support the use of the SCAT2, questions were raised regarding its sensitivity and specificity, which may have led to the creation of the SCAT3.[15,40]

Although Guskiewicz et al. presented a concise review of the evidence base upon which the SCAT3 was created,[14] it has been 3 years since this review and 8 years since the release of the SCAT2. Further, both the National Football League (NFL) and the National Hockey League (NHL) have used versions of the SCAT league-wide for sideline assessment of suspected concussion.[39] Given the increased use of the SCAT, we performed a systematic review of the current literature related to the SCAT and its objective components. The a priori objectives of the systematic review were to: 1) concisely summarize all published data on the 3 iterations of the SCAT, as well as its major components (the SAC and mBESS); 2) present aggregate normative data for the major components of the SCAT broken down by age and sex; and 3) identify areas for improvement for the next iteration of the SCAT.