Free-Cog Revisited: The Diagnostic Contribution of Cognitive and Executive Function

Abstract

Aim:

To examine Free-Cog, a recently described, hybrid screening instrument, as separate tests of cognitive (Free-Cog-Cog) and executive function (Free-Cog-Exec) to see if this improved screening accuracy for cognitive impairment compared with standard Free-Cog.

Materials & methods:

Free-Cog-Cog and Free-Cog-Exec were combined using Boolean logical ‘AND’ and ‘OR’ operators (serial and parallel combination), and also used to construct a stepwise decision tree.

Results:

Serial combination improved specificity and positive predictive value whereas parallel combination improved sensitivity, typical findings with these operators. Stepwise application identified groups with high and low probability of cognitive impairment but failed to differentiate adequately those in the intermediate uncertain diagnosis group.

Conclusion:

Study findings suggest limited benefit from reformulations of Free-Cog compared with the standard instrument.

Plain language summary

Dementia and cognitive impairment are common, but how best to identify these conditions remains uncertain. Many instruments which screen cognitive function have been described. Free-Cog is a relatively new screening instrument which tests both cognition and function; impairment in both constructs is required to fulfil agreed definitions of dementia. This study sought to examine whether dissociating the two elements of Free-Cog might produce more accurate screening for dementia and cognitive impairment. The separate tests were combined in series or in parallel, or used to create a decision tree. Examination of these two methods, using the dataset of a previous Free-Cog test accuracy study, suggested some benefits but also some losses compared with standard unitary Free-Cog test.

Keywords::

• Boolean operators
• decision tree
• dementia
• diagnosis
• Free-Cog
• mild cognitive impairment
• screening test

Financial disclosure

The authors have no financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

Competing interests disclosure

The authors have no competing interests or relevant affiliations with any organization or entity with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

Writing disclosure

No writing assistance was utilized in the production of this manuscript.

Ethical conduct of research

The authors state that they have obtained appropriate institutional review board approval or have followed the principles outlined in the Declaration of Helsinki for all human or animal experimental investigations. In addition, for investigations involving human subjects, informed consent has been obtained from the participants involved.