Evaluation of the NIH Toolbox Odor Identification Test in African American older adults with and without amnestic mild cognitive impairment

Background Early detection of amnestic mild cognitive impairment (aMCI), a prodromal stage of Alzheimer's disease (AD), is critical for timely intervention. Declines in olfactory function seem to be a promising, non-invasive indicator of AD pathology, but screening research in underrepresented groups is limited. Objective To evaluate the diagnostic discrimination and exploratory utility of the NIH Toolbox Odor Identification Test (NIHTB-OIT) in distinguishing healthy aging from aMCI in older African American adults. Methods Participants included 93 healthy agers (81.7% female; M age = 73.85, SD age = 5.06) and 52 individuals with aMCI (69.2% female; M age = 74.37, SD age = 5.26). NIHTB-OIT scores were analyzed using two-way ANCOVAs, controlling for age and education. Receiver Operating Characteristic (ROC) analysis assessed diagnostic utility. The optimal cut-off score was determined using the Youden index, which maximizes combined sensitivity and specificity. APOE ε4 status was examined in a subset of participants (64.8%). Results Healthy agers scored significantly higher than participants with aMCI ( p = 0.019), and females performed significantly better than males ( p = 0.031). ROC analysis demonstrated modest but significant discrimination with an Area Under the Curve (AUC) of 0.626 ( p = 0.010). Using a cut-off score of 5.5 resulted in 76.3% specificity and 40.4% sensitivity. No significant differences were observed by APOE ε4 status or diagnosis-by-sex interactions. Conclusions The NIHTB-OIT demonstrated modest discrimination between aMCI and healthy aging in African American older adults. Its brief administration time and high specificity support its potential as a rapid, low-burden adjunctive measure in community-based settings.