ORIGINAL ARTICLE

Statistical procedures for determining the extent of cognitive change following concussion

A Collie^1,2,3, P Maruff^2,4, M Makdissi³, M McStephen², D G Darby^1,2, P McCrory^3,5

¹ Center for Neuroscience, University of Melbourne, Parkville, Victoria, Australia
² CogState Ltd, Carlton South, Victoria, Australia
³ Centre for Health, Exercise and Sports Medicine, University of Melbourne
⁴ School of Psychological Science, La Trobe University, Bundoora, Victoria, Australia
⁵ Brain Research Institute, University of Melbourne

Correspondence to:
Correspondence to:
Dr Collie
68 Molesworth Street, North Melbourne 3051, Victoria, Australia; acollie{at}cogstate.com

Neuropsychological (NP) testing is now often used to help to determine if the cognitive function of a concussed athlete has declined. The NP test score after concussion is compared with the baseline test score. Many clinicians simply subtract one from the other and make a clinical decision about the significance or otherwise of the resulting "difference score". Such techniques are inadequate, as they fail to account for the many factors that may confound interpretation of serially acquired cognitive test scores. This is a review of a number of alternative approaches used in other areas of medicine for differentiating "true" changes from changes caused by these confounding factors. A case example is used to illustrate the effect that the statistical approach may have on clinical decision making.

Keywords: concussion; neuropsychology; statistics; cognition; brain

Abbreviations: DSST, digit symbol substitution test; NP, neuropsychological; RCI, reliable change index; TMT, trail making test

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