Background: The prevalence of cognitive impairment is increasing due to the aging population, and early detection is essential clinically. The Ascertain Dementia 8 (AD8) questionnaire is a brief informant-based measure recently developed to assess early cognitive impairment, however, its overall diagnostic performance is controversial. The objective of this meta-analysis was to assess the diagnostic accuracy of the AD8 for cognitive impairment.
Methods: All relevant studies were collected from databases including MEDLINE, EMBASE and the Cochrane Library up to April 2017. We used QUADAS-2 to assess the methodological quality after the systematic search. The accuracy data and potential confounding variables were extracted from the eligible studies which included those in English and non-English. All analyses were performed using the Midas module in Stata 14.0 and Meta-DiSc 1.4 software.
Results: Seven relevant studies including 3728 subjects were collected, and classified into two subgroups according to the severity of cognitive impairment. The overall sensitivity (0.72, 0.91) was superior to specificity (0.67, 0.78). The pooled negative likelihood ratio (0.17, 0.13) was better than the positive likelihood ratio (2.52, 3.94). The areas under the summary receiver operating characteristic curve were 0.83 and 0.92, respectively. Meta-regression analysis showed that location (community versus non-community) may be the source of heterogeneity. The average administration time was less than 3 minutes.
Conclusion: Our findings suggest that the AD8 is a competitive tool for clinically screening cognitive impairment and has an optimal administration time in the busy primary care setting. Subjects with an AD8 score ≧2 should be highly suspected to have cognitive impairment and a further definite diagnosis is needed.