Supplementary Material for: The clock is not enough: The Clock Drawing Test versus the Kimberley Indigenous Cognitive Assessment for detecting dementia in older Aboriginal and Torres Strait Islander adults

Aims
To explore performance of the Kimberley Indigenous Cognitive Assessment – Cognitive component (KICA-Cog) and the Clock Drawing Test (CDT) in people with dementia and without dementia in the Let’s CHAT Dementia study cohort.

Methods
In this cross-sectional diagnostic test accuracy study, Aboriginal and Torres Strait Islander older adults completed Comprehensive Geriatric Assessments. Demographic, health, cognitive and function histories, and cognitive assessments (KICA-Cog and CDT) were recorded. The reference standard was consensus diagnosis by two geriatricians blinded to KICA-Cog and CDT performance. Binary logistic regression and Receiver Operating Characteristic curve analyses explored accuracy against a diagnosis of dementia.

Results
Seventy-five adults with median age 74 years [interquartile range 65, 78] were assessed, of whom 39 (52.0%) were women. Forty-seven (62.7%) had normal cognition, 15 (20.0%) had Cognitive Impairment No Dementia (CIND) and 13 (17.3%) had dementia. Sixty-one (81.3%) participants had completed primary school and 13 (17.3%) had completed secondary school. People with dementia were older (p=.046), but no differences were found for gender, comorbidities or education. KICA-Cog and CDT scores were inversely associated with dementia in unadjusted and fully adjusted models (adjusted odds ratio [OR]=0.43, 95%CI [0.26–0.71] and OR = 0.18 [0.07–0.51], respectively). The KICA-Cog was superior to the CDT for classifying dementia in participants, with area under the curve [AUC] (95%CI) = 0.98 (0.95–1.00); versus 0.79 (0.64–0.93), respectively, p<.001. The optimal KICA-Cog cutpoint for classifying dementia was ≤34, with 92.3% sensitivity and 90.3% specificity.

Conclusions
KICA-Cog is superior to CDT at classifying dementia when used with older Aboriginal and Torres Strait Islander adults and should therefore be prioritised over the CDT for cognitive screening in older Aboriginal and Torres Strait Islander peoples.