Determine the performance of the RUDAS brief cognitive test (BCT) and its domains on the diagnosis of mild cognitive impairment (MCI) and dementia in illiterate individuals in Lima, Peru.

Most BCTs have been validated based on their total scores, however, domain analysis may help in the identification of different cognitive profiles and the diagnosis of specific dementias. RUDAS evaluates multiple domains and is not influenced by education or language, making it suitable for diagnosis in illiterate individuals.

We performed a secondary analysis of a cohort of randomly selected illiterate individuals, recruited for validation of RUDAS in Lima, Peru. Patients were evaluated in steps: screening (MMSE and PFAQ), diagnosis (Hachinski scale, PFAQ2, Beck Depression Inventory), and classification (CDR and DSM-V criteria). RUDAS was applied during the second stage and was not used for patient selection. We compared BCT scores using the T-test and ANOVA. We correlated each RUDAS domain to the BCTs and CDR scores using a Spearman correlation coefficient. For diagnostic performance, we used a Receiver Operating. 

We included 187 patients (64 controls, 60 MCI, and 63 dementia patients). Average RUDAS score 23,87 ± 0,93, 20,43 ± 1,39 and 14.97 ± 2,21, respectively. Differences were statistically significant between groups for all domains, except for ideomotor praxis and visuospatial praxis. Domains were correlated to MMSE by 0.86, PFAQ by 0.83, and CDR by 0.86. The total RUDAS score had an AUC of 98% (IC95 96-100%) for both MCI and dementia. By domains, judgment, verbal fluency, and memory had acceptable discrimination.

We found that RUDAS had an excellent diagnostic performance for MCI and AD in illiterate individuals. While its domains individually found statistically significant differences between patients, they did not reach the level of diagnostic capacity the total score had.