Comparison of 2 informant questionnaire screening tools for dementia and mild cognitive impairment: AD8 and IQCODE

Dementia and mild cognitive impairment (MCI) are underrecognized in community settings. This may be due in part to the lack of brief dementia screening tools available to clinicians. We compared 2 brief, informant-based screening tests: the AD8 and the Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE) in a community-based neurology practice in the midwestern United States.

We examined 186 consecutive patients (44 controls, 13 with MCI, and 129 with dementia). Receiver operator characteristic curves were used to examine the ability of AD8 and IQCODE to discriminate between controls and MCI or dementia. Sensitivity, specificity, predictive values, and likelihood ratios were reported.

AD8 differentiated healthy controls from MCI (P<0.001) or dementia (P<0.001), and MCI from dementia (P=0.008). The IQCODE differentiated controls and MCI from dementia (both P<0.001), and between controls and MCI (P=0.002). Both AD8 (AUC=0.953; 95% confidence interval, 0.92-0.99) and IQCODE (AUC=0.930, 95% confidence interval, 0.88-0.97) provided discrimination between controls and patients with dementia; however, the AD8 had superior sensitivity detecting dementia (99.2%) and MCI (100%) compared with the IQCODE (79.1% for dementia, 46.1% for MCI) with nonoverlapping confidence intervals. Using published cut-offs (AD8≥2, IQCODE≥3.4), only 1 case of dementia was missed with the AD8, whereas the IQCODE failed to detect dementia in 27 individuals. The AD8 detected MCI in all 13 individuals, whereas the IQCODE misclassified 7 individuals.

Both the AD8 and IQCODE were able to detect dementia in a community setting. The AD8, however, was more successful than IQCODE in detecting MCI. If simple and efficient screening for early cognitive impairment is the goal, particularly in the early stages (e.g., for prevention trials or public screening), the combination of an informant interview (the AD8) and a brief performance measure could be considered as they meet the basic requirements of the Personalized Prevention Plan for Medicare beneficiaries.