Free-Cog: Pragmatic Test Accuracy Study and Comparison with Mini-Addenbrooke's Cognitive Examination

Abstract

Background/aims: Canonical definitions of the dementia construct encompass deficits in both cognition and function, but most screening instruments for possible dementia address only cognitive abilities. Free-Cog is a recently described brief screening instrument for dementia designed to address not only cognitive but also functional abilities.

Methods: A pragmatic test accuracy study of Free-Cog was undertaken in consecutive patients seen over 1 year in a secondary care setting. The performance of Free-Cog for diagnosis of dementia and mild cognitive impairment (MCI) was compared to that of Mini-Addenbrooke's Cognitive Examination (MACE).

Results: In a cohort of 141 patients (prevalence of dementia and MCI 11 and 32%, respectively) both Free-Cog and MACE were quick and easy to use and acceptable to patients. Both tests had high sensitivity (1.00) and large effect sizes (Cohen's d) for diagnosis of dementia, but Free-Cog was more specific. For diagnosis of MCI, Free-Cog lacked sensitivity (0.58) but was specific (0.81), whereas MACE was sensitive (0.91) but not specific (0.35). Weighted comparison suggested equivalence for dementia diagnosis but a net benefit for MACE regarding MCI diagnosis.

Conclusion: Free-Cog is an acceptable and accurate test for dementia screening in a dedicated cognitive disorders clinic, but it appears less sensitive than MACE for the identification of MCI.

Keywords: Dementia; Diagnosis; Free-Cog; Mild cognitive impairment; Mini-Addenbrooke’s Cognitive Examination; Sensitivity; Specificity.