Cognitive Screening in Older People Using Free-Cog and Mini-Addenbrooke’s Cognitive Examination (MACE)

Abstract

Ageing is the strongest known risk factor for many of the neurodegenerative diseases causing cognitive decline and dementia. Identification of cognitive impairment may be a prelude to appropriate treatment, hopefully disease-modifying. Use of cognitive screening instruments may be an equitable way to identify cognitive impairment. This study examined the use of two such instruments, Free-Cog and Mini-Addenbrooke’s Cognitive Examination (MACE), in patient cohorts referred to a dedicated cognitive disorders clinic based at a tertiary neurosciences centre. Results showed that: (1) specificity and positive predictive value increased with patient age for both tests with some loss of sensitivity and negative predictive value. (2) In the oldest age groups (≥75 and ≥70 years respectively) where specificity was at maximum, a positive test result (i.e. below the specified test cut-off) rules in the diagnosis of cognitive impairment. (3) Values of an “Efficiency Index” for each test indicated qualitatively a moderate change in the probability of correct diagnosis and quantitatively an approximately 15-25% increase in the probability of correct diagnosis. These findings show that both Free-Cog and MACE may be used with confidence for the identification of cognitive impairment and dementia in older patient cohorts. These findings may have implications for public health policies directed to case-finding in clinical practice as opposed to population-based screening.

Efficiency Index for Binary Classifiers: Concept, Extension, and Application

“…It has been suggested [3,4] that the EI may effectively communicate risk to both clinicians and patients and their families, specifically the risk of correct diagnosis versus misdiagnosis for a particular test, in a way that is more transparent than for sensitivity, specificity, predictive values, and likelihood ratios. The EI values have been calculated for various cognitive screening instruments [3,4,12]. This measure may be of particular value when the administration of invasive tests or tests associated with morbidity and even mortality are being proposed.…”

“…Balanced and unbiased EI measures were previously introduced to try to take into account the values of P and Q [4]. In these and other studies, the EI values have found application in the assessment of cognitive screening instruments used in the assessment of patients with memory complaints [3,4,12]. The aims of the current paper were twofold: firstly, to extend the EI construct to other formulations, namely "balanced level" and "quality" variants; and secondly, to apply all the described EI variants, both previously described (standard, balanced, unbiased [3,4]) and new (balanced level, quality) to the dataset of a large prospective test accuracy study of a cognitive screening instrument, the Mini-Addenbrooke's Cognitive Examination.…”