Objective: To compare the Symbol Digit Modalities Test (SDMT) to the King-Devick (K-D) test as a potential rapid sideline screening for concussion.

Background: Sports-related concussion is increasingly recognized as a major public health problem due to potential for neurologic sequelae. Despite recent research that has suggested the potential role of the K-D test as a sideline screening tool for concussion, there remains a need for a rapid sideline test that requires less examiner attention. The K-D test screens for combined impairments in eye movements, attention and language by measuring the speed of rapid number naming on 3 test cards. The written version of the SDMT is based on measurement of the speed of conversion of geometric designs into number responses, and captures impairments of attention, processing speed, eye movements, writing, and other correlates of cerebral dysfunction.

Methods: The SDMT and K-D test were administered pre- and postfight by a single examiner to 16 mixed martial arts fighters. Changes in SDMT and K-D scores from pre- to postfight were compared for those with head trauma during the fight vs. those without.

Results: There was a modest correlation between head trauma during the match and whether there was worsening (increase) in K-D scores (r=0.54, p=0.015), the actual change (r=0.42, p=0.055) and the percentage change in K-D scores from pre-to postfight (r=0.50, p=0.025). Only 1 fighter without head trauma had a worsening of K-D score by ≥ 5 seconds. There was only small to medium correlation between worsening of SDMT score (decrease) and K-D score. Surprisingly there was no correlation between SDMT scores and concussion during the match.

Conclusions: This study confirms that the K-D test, but not the SDMT, is reliable in rapidly identifying athletes with head trauma. This suggests that further validation of the K-D test, but not the SDMT, may be valuable in the early detection of concussion.

Summary Points:

  • Compared K-D scores and Symbol Digit Modalities Test (SDMT) scores among 16 mixed martial arts fighters, pre- and post-fight.
  • There was an overall worsening of K-D scores in fighters with head trauma.
  • There was no correlation between SDMT scores and concussion during the match.
  • The K-D test was more reliable in identifying a change elicited by head trauma in this cohort compared to the SDMT.
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