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Abstract
Background Concussion head injuries are common in high school athletes. The Sport Concussion Assessment Tool – 2 (SCAT2) has been recommended and widely adopted as a standardised method of evaluating an injured athlete with a suspected concussion. Sideline return to play decisions can hinge on the results of a SCAT2 score. However, most athletes will not have had baseline testing performed for comparison if injury occurs. Therefore, establishing of age-, sex- and sport-matched normative data for the high school athlete population is critical.
Purpose To determine baseline scores in all SCAT2 domains among high school athletes with no prior history of a concussion and to examine subgroup differences for girls and boys, age and sport to establish normative ranges.
Materials and methods The SCAT2 was administered to 214 high school athletes (155 males and 59 females) who participated in football, women's soccer, men's basketball, gymnastics, baseball, softball and track with no prior history of concussion. There were 111 athletes in the 13–15-year-old cohort and 103 in the 16–19-year-old group with a mean age of 15.7 years of age. In all SCAT2 domains the mean and SD of the results were determined. The domains were analysed using age, sex and sport as covariates. Component parts of the cognitive (concentration) domain (digit sequencing and months of year in reverse order) were also analysed by age, sex and sport. The percentage of high school athletes able to perform each digit-sequencing test was calculated as was the percentage of participants who could recite the months of the year in reverse order.
Results The average SCAT2 score for these high school athletes was 89 of a possible 100 with a SD of 6 units. Athletes reported two or three symptoms at baseline with older students reporting more symptoms than younger ones. The average balance score was 25.82 (of 30), and all athletes were able to complete the double-leg stance. Females scored significantly higher on the balance, immediate memory and concentration scores. Concentration scores in non-concussed high school athletes were low. Only 67% of high school athletes could recite the months of the year backward and only 41% could correctly sequence 5 digits backward. Only 55% of high school football players could correctly recite the months of the year backward and 32% could sequence 5 digits.
Conclusions Non-concussed high school athletes scored near the total possible in most domains of the SCAT2 with the exception of concentration testing and balance testing. All athletes were able to complete the double-leg stance at baseline; however, there was significant variability of tandem and single-leg stance. Baseline testing is important when considering balance tests. Concentration testing in high school athletes is unreliable because of high baseline error and is likely to result in a high rate of false positives and false negatives. Return to play decisions should not rely on concentration testing without a baseline test for comparison.
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Introduction
Concussions are a common sports injury among high school athletes, with a recent review estimating up to 3.8 million recreation- and sport-related concussions annually.1
The Sport Concussion Assessment Tool – 2 (SCAT2) was developed at the Third International Conference on Concussion in Sport in Zurich in 2008 as an objective tool to help guide practitioners when making return-to-play decisions for athletes aged 10 years and older who may have suffered a concussion.2 The SCAT2 is a non-computerised neurocognitive assessment, which has a subjective and a objective portion. The subjective portion consists of a 22-item postconcussion symptom score, which is graded 0–6 for severity. The objective portion includes physical signs, Glasgow coma scale, a balance examination, a coordination examination and a cognitive assessment, which includes orientation, immediate memory, concentration and delayed recall. A score is assigned for each section, with a total possible score of 100. (SCAT2 card is publically available at www.cces.ca/en/files-116 and has a recent iPad application.)
Scores of the SCAT2 must be evaluated in the context of what is normal for the athlete by comparing with either an individual baseline test or to normative data. Schneider et al3 reported normative data on the original SCAT developed at the Second International Concussion Consensus Conference4 for youth hockey players aged 9–17 years. The SCAT is an earlier version of the SCAT2 and scores are not comparable. There are currently no baseline normative data for the SCAT2 among high school athletes. The purpose of this study was to determine SCAT2 baseline scores among high school athletes with no prior history of a concussion and to examine subgroup differences for girls and boys, age and sport.
Methods
Participants
This prospective study included high school student athletes of both genders from nine of the thirteen Seattle Public High Schools and NW Soccer Camps. Two schools were excluded because they did not offer competitive sports; two schools were excluded because their athletic trainers worked in a different system. Three sessions of NW Soccer Camps, including a regional western Washington summer soccer skills camp, were included for diversity in the sample. The study was approved by Seattle Children's Hospital Institutional Review Board, Seattle public schools and the directors of NW Soccer Camps. The sports teams that participated in this study were football, women's soccer, men's basketball, gymnastics, baseball, softball and track. Participation criteria at the Seattle schools included (1) students in active sports participation, (2) no history of concussion within the previous 6 months, (3) no history of learning disabilities or attention deficit disorder and (4) a signed parental consent form. At each school, athletic trainers obtained the student team rosters at the beginning of the season and identified potential participants. At NW Soccer Camps, inclusion criteria were identical to the above and included camp participants between 14 and 19 years.
Testing and statistical analysis
Data were collected prospectively over 2 academic years at the Seattle public schools (2008–2009 and 2009–2010) and during 2010 summer enrollment at NW Soccer Camps. All athletic trainers (ATCs) attended an instruction session to standardise administration of the SCAT2. In the preseason, athletic trainers screened students for eligibility and administered the SCAT2 to each eligible athlete in a quiet setting prior to a practice session.
Descriptive statistics were used to assess the data. Each domain of the SCAT2 was evaluated for mean and SD in score results. All participants were concussion-free and did not have loss of consciousness or balance problems related to concussion. Thus, a physical sign score of 2 was assigned to all subjects, and this was included in the final SCAT2 tally for consistency in scoring. The total score possible on the baseline was 100 (table 1).
SCAT2 results summary
In all SCAT2 domains the mode, mean and SD of the results were determined. The proportion of participants reporting each symptom were reviewed and analysed using age, gender and sport as covariates. Within the cognitive composites, the component parts of the domains were analysed. The percentage of high school athletes able to perform each digit-sequencing test was calculated as was the percentage of participants who could recite the months of the year in reverse order. Statistical analysis was performed using STATA 10 (StataCorp. 2007. Stata Statistical Software: Release 10. College Station, Texas, USA: StataCorp LP). Comparison between female and male students was performed using the Mann–Whitney U test (two-sample Wilcoxon rank-sum test). Kruskal–Wallis one-way analysis of variance for non-parametric data was used to compare significant differences between students participating in different sports.
Results
This study included 214 participants with a mean age of 15.71 years (range 13–19 years) with a total of 59 females and 155 males. Baseline SCAT2 scores were analysed as a group and stratified based on age, sex and sport. Age of subgroups were 13–15 years and 16–19 years. Results are shown in tables 1 and 2.
SCAT2 scores summarised by age and sex
Symptom score
The SCAT2 symptom score is calculated by subtracting the number of symptoms reported from the maximum possible (22). A higher symptom score is consistent with fewer symptoms. On average, male students exhibited slightly fewer symptoms (mean of 19.79) than for their female counterparts (mean of 19.64), although this was not statistically significant (p=0.38). By age cohort, younger females (13–15 year-olds) exhibited fewer symptoms than their male counterparts (p=0.02). Segregated by age, the younger age group (13–15 years) exhibited a trend towards fewer symptoms than the 16–19-year age group (symptom score=20.32 vs 19.14, respectively; p=0.06). The most frequent symptoms included fatigue or low energy (24%), trouble falling asleep (21 %), difficulty concentrating (19 %), difficulty remembering (17%) and being nervous or anxious (16%) (figure 1). Fifty-two per cent of females reported no symptoms compared with 40% of males. Twenty-five per cent of females reported one to three symptoms at baseline, while the number for males was 35%. Although the average symptom score of males was slightly higher than females (indicating fewer symptoms on average), there were more females who reported having no or few symptoms. Among the younger cohort (13–15 year-olds), the females reported being asymptomatic at baseline significantly more frequently than the males (66% vs 39%). For the 16–19-year-old cohort, the gender difference in being asymptomatic was less striking (43% females vs 40% of males) (figure 2).
Reported symptoms by gender.
Percentage of number of reported symptoms by sex.
Glasgow Coma Scale
All subjects scored 15 points on this section of the assessment.
Balance
All athletes evaluated made no errors when completing the double-leg stance. Single-leg stance gave the most errors, with an average of 3.05 of 10. Tandem stance gave an error rate of 1.17 of 10. Total balance examination score was 25.82 of a possible 30 (table 1).
Female students scored significantly better in the balance composite (p=0.01). They had fewer errors in single-leg stance and tandem stance (mean of 2.37 of 10 errors and 0.92 of 10 errors, respectively) than their male counterparts (mean of 3.31 of 10 errors and 1.27 of 10 errors, respectively). Their total balance score (maximum of 30) was 26.85 compared with that of males, 25.43 (table 2).
The discrepancy between males and females is larger in the younger cohort. Females in the age group of 13–15 years had a total balance score of 27.41 compared with males, 25.25 (p=0.00), while females in the 16–19-year group scored 26.38 and males scored 25.65 (p=0.58.) (table 3).
Balance score summary
Coordination
Ninety per cent of all athletes of all ages were able to successfully complete the coordination test (table 1).
Orientation
Overall, subjects scored 4.79 of a possible 5.00. Although females scored higher than males in all age groups, the difference was not statistically significant. There was a slight decrease in scoring for boys in the age of 13–15 years (4.67). Girls at all ages and older boys had similar scores (4.85–4.88) (table 2).
Immediate memory
Forty-five per cent of all athletes were able to recall all 15 objects. Females scored higher than males (14.31 vs 13.64; p=0.00). Age and gender analysis (table 2) show the lowest score in boys of age 16–19 years (13.55) and highest score in older girls (14.44). Significant differences were also noted among the age cohorts. For age group of 13–15 years, females scored 14.15 and males scored 13.71; p=0.04. In the 16–19 year-olds, females scored 14.44 and males scored 13.55; p=0.02.
Concentration score
The average total concentration for the entire study was 2.96 of 5. Males aged 13–15 years scored the lowest (2.67) and girls aged 16–19 years scored the highest (3.63). Females scored higher for the total sample as well within the age groups. This difference was statistically significant for all age groups as well for the 16–19-year age group (p=0.01 for all ages; p=0.21 for age 13–15 years; p=0.03 for age 16–19 years) (table 2).
Digits backwards
The percentages of participants able to recite 3, 4, 5 and 6 digits in reverse order are shown in table 4. Overall, 93.93% were able to recite 3 digits backwards, 76.64% recite 4 digits, 41.12% recite 5 digits and only 17.29 % were able to recite 6 digits in reverse order. Female students performed the test more accurately than males in age groups. One hundred per cent of younger females (13–15 year-olds) were able to recite 3 digits backwards but only 89% of older males (16–19 year-olds) were able to complete this task, although the difference is not significant.
Concentration score summary by age, sex and overall total
Months in reverse order: Only 67% of high school athletes were able to recite the months of the year backwards at baseline. Older females also did considerably better recalling months of the year in reverse order. A total of 84.38% females between 16–19 years of age succeeded in this task compared with 70.42% of their male counterparts. Among the younger group, 59.26% of females succeeded in recalling the months of the year in reverse order compared with 57.14% of their male counterparts (table 4).
Delayed recall
The average score for delayed recall was 3.96 of possible a score of 5. Notably, younger students (13–15 year-olds) scored higher than the older group (16–19 year-olds) for boys and girls. (table 2) The difference between the two age groups however is not statistically significant. Older females of age 16–19 years had the lowest score (3.72).
Total score
The total was 88.99 with a SD of 5.95. Females scored higher than males (90.81 vs 88.39, respectively). This was statistically significant (p=0.00). Females also scored higher than males in both age groups. This difference was statistically significant for the younger age group (13–15-year-old females, 92.33 and males, 88.37; p=0.00) but not for 16–19 year-olds (16–19-year-old females, 89.55 and males, 88.28; p=0.19). Females of age 13–15 years scored the highest overall with a score of 92.33.
SCAT2 by sports
The comparisons of SCAT2 scores according to sports participation are shown in table 5. Baseball, track and football players have the lowest scores (87.09, 87.29 and 87.72, respectively). Soccer, softball, gymnastics and basketball players have the highest (92.17, 91.6, 90.5 and 89.65, respectively). Due to the varying number of participants from each sport, statistical analysis results are not valid. Concentration scores by sport are shown in table 6.
SCAT2 scores by sport
Concentration score by sport participation
Discussion
The SCAT2 has been recommended and widely adopted as a standardised method of evaluating an injured athlete with a suspected head injury or concussion. Sideline return to play decisions can hinge on the results of a SCAT2 score. However, most athletes will not have had baseline testing performed for comparison after injuries. Therefore, establishment of age-matched normative data is critical.
To date there have been a number of assessment tools proposed for use in the assessment of sport-related concussion. However, few have been validated, particularly for youth populations. The Maddocks questions have been shown to be a reliable indicator of orientation and recent memory. The questions have been validated in professional Australian football players; an older age cohort.5 6 However, because these questions ask specifics about game time details, they were not used in this baseline testing. Although Maddocks questions are asked during administration of the SCAT2, they are not included in the total score. The Standardised Assessment of Concussion (SAC) was developed in 1997 by McCrea and has also been validated.7,–,9 In addition, balance testing in concussion appears to be valid; however, there is debate regarding test–retest reliability.10,–,17 These validated tests account for only 35 of the possible 100 points on the SCAT2.
The average baseline SCAT2 score for non-concussed high school athletes in this study is 88.9. This is an important consideration when deciding whether to hold a player out or return to play. Based on the study results, the ‘total score’ for an average high school athlete would be considered to be about 90 with a SD of 6 units. This study also shows considerable variation of normal for SCAT2 testing in high school athletes. Scores from 83 to 95 are statistically likely to be within a normal range (1 SD from the mean). In general, postconcussion examinations in high school athletes without a baseline assessment which are below 83 (1 SD) or 77 (2 SDs) are potentially abnormal and should undergo more thorough evaluation before returning to play.
However, a contributing factor in the overall score results is that less than half of non-concussed high school athletes could repeat 5 or 6 digits backwards (41% and 17%, respectively). Only 67% of non-concussed athletes could recite the months of the year backwards and only 77% could repeat 4 digits backwards. The high rate of failure on these tests of non-concussed athletes suggests that these components are not accurate discriminators of concussion without an individual baseline test. Reliance on normative data would result in a high rate of false-positive and false-negative scores.
When evaluating a concussion, symptoms are among the initial indicators assessed. However, it is clear that some athletes, and non-athletes will report symptoms commonly used to assess concussion when they have not suffered head injury.18 This study showed that normal high school students had a preinjury baseline symptom score of 19.75 of a total possible 22. In general, there should be a higher index of suspicion for concussion when a high school athlete presents with more than a few symptoms. Overall, males had fewer symptoms than females. Shehata et al19 and Covassin et al20 also found adult women had higher baseline symptoms. In the study of youth hockey players, Schneider et al3 found that non-concussed female players of age 13–14 years showed fewer symptoms than male players of the same age. This study also showed younger female athletes (13–15 year-olds) had a decreased number of symptoms compared with their male counterparts.
Shehata et al19 and Schneider et al3 found the most commonly reported baseline symptom to be fatigue or low energy for both sexes, which is consistent with our findings. Trouble falling sleep, difficulty concentrating and difficulty remembering were symptoms which are also ranked highly at baseline. Recently much focus has been given on vestibular function and balance as markers of concussion.11,–,17 21,–,25 This study showed that dizziness is a relatively uncommon symptom found in only 5% of non-concussed high school athletes.
The SCAT2 uses a modified version of the Balance Error Scoring System (BESS) which includes the single-leg stance. Variations of balance tests, particularly the BESS have been widely studied and validated.10,–,14 16 Recently, Finnoff et al have examined the intrarater and interrater reliability of balance tests and concluded that only the firm single-leg subcategory of the balance test is valid when different scorers are used.17 In this study, all high school athletes at baseline can perform double-leg stance without error. Further follow-up testing in concussed athletes will help determine which, if any, of the balance tests can best identify athletes with concussion injury. If a high school athlete on the sideline cannot perform a double-leg stance without error, suspicion for concussion should be high.
There are several limitations to this study. First, this study enrolled 214 student athletes and included only the Seattle area, thus limiting the generalisability of the results. A larger sample with national representation would provide more significant baseline data. Although all ATCs had a training session to facilitate consistent administration of the assessment, there may have been some differences among testing methods. However, this approximates real-world administration of the SCAT2. Similarly, an environment free of distractions might not have been possible during all testing situations. In addition, the uneven number of female and male participants in the sample may have skewed the results. Finally, the baseline tests were only performed once. It is unclear if baseline tests are consistent between sessions, if there is individual variability, or significant learning effect.
Previously there has been no normative data published on SCAT2 testing in high school athletes. This research shows baseline variability among age groups, gender and sports that should be taken into account when evaluating the SCAT 2 in concussed students. Specifically, the average SCAT2 score for non-concussed high school athletes is about 90. Non-concussed high school athletes should score near the total possible in most domains of SCAT2 with the exception of concentration testing and balance testing. Concentration testing in high school athletes using the SCAT2 is likely to result in a high rate of false-positives and false-negatives and may be unreliable for return to play decisions without a baseline test. Likewise, the baseline balance showed significant individual variability.
Acknowledgments
The authors thank the Seattle School District's Certified Athletic Trainers. Without their help and hard work this research would not have been possible. As regional healthcare providers, the authors are indebted to the athletic trainers for ensuring the health and safety of student athletes throughout out the Seattle area.
References
Footnotes
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Funding Academic Enrichment Fund – Seattle Children's Hospital.
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Competing interests None.
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Ethics approval Seattle Children's IRB.
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Provenance and peer review Not commissioned; externally peer reviewed.