Free-Cog reformulated: analyses as independent or stepwise tests of cognitive and executive function

Abstract

AbstractFree-Cog is a recently described, hybrid screening instrument incorporating tests of cognitive and executive function. In this study, Free-Cog was reformulated as separate tests of cognitive function and executive function to examine whether this might improve screening accuracy for cognitive impairment (dementia and mild cognitive impairment) compared to the standard, unitary Free-Cog. The two separate tests, designated “Free-Cog-Cog” and “Free-Cog-Exec,” were either combined using the Boolean logical “AND” and “OR” operators (serial and parallel combination) or used to construct a stepwise decision tree. Serial combination improved specificity and positive predictive value whereas parallel combination improved sensitivity, findings typically observed when applying these operators. Stepwise application identified groups with high and low probability of cognitive impairment but failed to adequately differentiate those in the intermediate uncertain diagnosis group. Although the dataset used was relatively small, the findings of this study suggest little benefit for reformulations of Free-Cog compared to the standard, unitary instrument.