Addenbrooke's Cognitive Examination III (ACE-III) and mini-ACE for the detection of dementia and mild cognitive impairment

Background

The number of new cases of dementia is projected to rise significantly over the next decade. Thus, there is a pressing need for accurate tools to detect cognitive impairment in routine clinical practice. The Addenbrooke's Cognitive Examination III (ACE‐III), and the mini‐ACE are brief, bedside cognitive screens that have previously reported good sensitivity and specificity. The quality and quantity of this evidence has not, however, been robustly investigated.

Objectives

To assess the diagnostic test accuracy of the ACE‐III and mini‐ACE for the detection of dementia, dementia sub‐types, and mild cognitive impairment (MCI) at published thresholds in primary, secondary, and community care settings in patients presenting with, or at high risk of, cognitive decline.

Search methods

We performed the search for this review on 13 February 2019. We searched MEDLINE (OvidSP), Embase (OvidSP), BIOSIS Previews (ISI Web of Knowledge), Web of Science Core Collection (ISI Web of Knowledge), PsycINFO (OvidSP), and LILACS (BIREME). We applied no language or date restrictions to the electronic searches; and to maximise sensitivity we did not use methodological filters. The search yielded 5655 records, of which 2937 remained after we removed duplicates. We identified a further four articles through PubMed 'related articles'. We found no additional records through reference list citation searching, or grey literature.

Selection criteria

Cross‐sectional studies investigating the accuracy of the ACE‐III or mini‐ACE in patients presenting with, or at high risk of, cognitive decline were suitable for inclusion. We excluded case‐control, delayed verification and longitudinal studies, and studies which investigated a secondary cause of dementia. We did not restrict studies by language; and we included those with pre‐specified thresholds (88 and 82 for the ACE‐III, and 21 or 25 for the mini‐ACE).

Data collection and analysis

We extracted information on study and participant characteristics and used information on dementia and MCI prevalence, sensitivity, specificity, and sample size to generate 2×2 tables in Review Manager 5. We assessed methodological quality of included studies using the QUADAS‐2 tool; and we assessed the quality of study reporting with the STARDdem tool.

Due to significant heterogeneity in the included studies and an insufficient number of studies, we did not perform meta‐analyses.

Main results

This review identified seven studies (1711 participants in total) of cross‐sectional design, four examining the accuracy of the ACE‐III, and three of the mini‐ACE. Overall, the majority of studies were at low or unclear risk of bias and applicability on quality assessment. Studies were at high risk of bias for the index test (n = 4) and reference standard (n = 2). Study reporting was variable across the included studies. No studies investigated dementia sub‐types. The ACE‐III had variable sensitivity across thresholds and patient populations (range for dementia at 82 and 88: 82% to 97%, n = 2; range for MCI at 88: 75% to 77%, n = 2), but with more variability in specificity (range for dementia: 4% to 77%, n = 2; range for MCI: 89% to 92%, n = 2). Similarly, sensitivity of the mini‐ACE was variable (range for dementia at 21 and 25: 70% to 99%, n = 3; range for MCI at 21 and 25: 64% to 95%, n = 3) but with more variability specificity (range for dementia: 32% to 100%, n = 3; range for MCI: 46% to 79%, n = 3). We identified no studies in primary care populations: four studies were conducted in outpatient clinics, one study in an in‐patient setting, and in two studies the settings were unclear.

Authors' conclusions

There is insufficient information in terms of both quality and quantity to recommend the use of either the ACE‐III or mini‐ACE for the screening of dementia or MCI in patients presenting with, or at high risk of, cognitive decline. No studies were conducted in a primary care setting so the accuracy of the ACE‐III and mini‐ACE in this setting are not known. Lower thresholds (82 for the ACE‐III, and 21 for the mini‐ACE) provide better specificity with acceptable sensitivity and may provide better clinical utility. The ACE‐III and mini‐ACE should only be used to support the diagnosis as an adjunct to a full clinical assessment. Further research is needed to determine the utility of the ACE‐III and mini‐ACE for the detection of dementia, dementia sub‐types, and MCI. Specifically, the optimal thresholds for detection need to be determined in a variety of settings (primary care, secondary care (inpatient and outpatient), and community services), prevalences, and languages.