Discriminant Construct Validity of ImPACT™: A Companion Study

In a previous analysis of ImPACT scores relative to traditional neuropsychological tests (NP) and experimental tasks (Maerlender et al., 2010) we demonstrated convergent construct validity for the primary ImPACT test-score composites. A complete analysis of discriminant validity was not undertaken at that time. Here, test scores from the 54 collegiate football and hockey players were re-analyzed to specifically address the discriminant validity of the ImPACT composite scores using a multiply operationalized correlation matrix of multi-trait multi-method data. In the method used here, discriminant validity is determined by obtaining non-significant correlations between a target score when correlated with the average of the other trait measurements (multiply-operationalized multi-trait-mono-method analysis). Results showed that the ImPACT Verbal Memory (p=.044), Visual Memory (p=.006), and Visual Motor Speed (p=.000) scores were highly correlated with composites of the other scores, while the Reaction Time composite demonstrated adequate discriminant validity (p=.145). In comparison all of the NP composites showed good discrimination (all p-values >.05, except for Reaction Time p=.05). Thus the apparent lack of discriminability between three of four composite scores in this sample raises questions about using ImPACT composite scores to support specific construct-oriented interpretations. Taken together, the discriminant and convergent construct validity properties of ImPACT indicate construct sensitivity, but limited construct specificity.