Comment on article: King‐Devick test reference values and associations with balance measures in high school American football players

I read with interest your recently published article in Scandinavian Journal of Medicine and Science in Sports (Alsalaheen et al., 2015). In paragraph two of that article, Alsalaheen et al. (2015) describe that “in order to quantify the effects of concussion, the performance of the King-Devick test must be compared with the pre-injury performance baseline. ” We know that to be a key part of the protocol to use the KingDevick test as a sideline indicator of concussions. More than 30 recent publications in peer-reviewed journals have supported that fact (Galetta et al., 2011a,b, 2013, 2015a,b; Dziemianowicz et al., 2012; King et al., 2012, 2013, 2014, 2015a,b; Duenas et al., 2013; Institute of Medicine 2013; Leong et al., 2013, 2015; Munce et al., 2013, 2014; Dhawan et al., 2014; Duenas & Jandial, 2014; Master et al., 2014; Silverberg et al., 2014; Spradley et al., 2014; Vartiainen et al., 2014; Ventura et al., 2014, 2015a,b,c; Benedict et al., 2015; Fischer et al., 2015; Hunt et al., 2015; Vernau et al., 2015). However, further in that paragraph, the article states that “In the absence of baseline scores, the clinical utility of the King-Devick test depends on the availability of reference values. ” We know that statement to be unsupported and completely in opposition to the King-Devick test’s protocol for use. The King-Devick test should not be used to evaluate the possibility of a concussion on the sidelines without a comparison to the subject’s own recent (within 12 months) pre-injury King-Devick test baseline. In fact, two studies have been published, which show that King-Devick test is not effective when using age-matched normative data and age-matched controls (Silverberg et al., 2014; Vartiainen et al., 2014). Instructions for the proper use of the KingDevick test are included with the test, and the instructions accurately state that a King-Devick test administered after suspected head trauma should only be used when comparing the subject to his/her own recent (within 12 months) pre-recorded KingDevick baseline score. The recommendation states in the article that the King-Devick test, as an alternative to comparison to the subject’s own recent baseline, depends on or should be compared with normative values is not only factually incorrect but the adoption of this procedure will lead to false negatives which could result in missing concussed athletes, returning them to play, and risking a repeated and potentially more devastating injury. For instance, there have been concussions recorded with a post-head trauma KingDevick test time of 30 s, when compared to the subject’s pre-injury baseline of 25 s. This subject’s concussion would have certainly have been missed by comparing a post-injury time of 30 s to normative or reference data because the subject’s baseline was faster than the average King-Devick test time. When utilized on the sidelines as a concussion screening tool along with recent subject baselines, the King-Devick test has been shown, in a large meta-analysis (Galetta et al., 2015a), to both have high sensitivity of 86% and specificity of 90% in detecting concussions. That is better sensitivity and specificity than many commonly relied upon screening/diagnostic tests used in clinical medicine. Because of all the facts described in all the peerreviewed published literature regarding King-Devick test as a sideline screening test for concussions, we do not endorse, recommend, or even accept using normative data or age-matched controls for concussion screening. An annual King-Devick test baseline is required for this test to be useful in these acute conditions.