# Visuospatial impairment in dementia: a new index to improve the clinical diagnosis of Alzheimer’s disease

## TL;DR

A new index called ReDCOOL improves the accuracy of diagnosing Alzheimer's disease by evaluating visuospatial test results.

## Contribution

The ReDCOOL index is introduced as a novel tool to enhance clinical confidence in diagnosing Alzheimer's disease.

## Key findings

- AD patients performed worst in visuospatial tests.
- The ReDCOOL index showed higher reliability in identifying AD (AUROC 0.729).
- The index is practical and does not extend clinical evaluation time.

## Abstract

The differential diagnosis between Alzheimer’s disease (AD) and other causes of dementia is essential but challenging. Therefore, there is an increasing need for early, reliable, and non-invasive tests to distinguish between different forms of dementia.

To determine whether neuropsychological tests assessing visuospatial function can improve confidence in the clinical diagnosis of AD.

Retrospective observational single-center cohort study involving all patients consecutively referred to our outpatient clinic for cognitive disorders who underwent neuropsychological assessment between 2013 and 2018. In addition to demographic and functional variables, each patient underwent neuropsychological tests to assess cognitive performance, memory, and executive, language, and visuospatial ability, according to clinical protocols. The clinical diagnosis of cognitive disorders, based on standard diagnostic criteria, served as the gold standard. Accuracy measures of visuospatial tests to diagnose AD were calculated. Additionally, a new index derived from the sum of four items (Rey-Osterrieth figure copying, Copy of Drawings, Clock Drawing Test, and years of schooling) was tested (ReDCOOL).

Of the 342 patients analyzed, 308 were diagnosed with dementia or mild cognitive impairment, including 60 with AD. AD patients exhibited the worst performance in visuospatial tests, and the utilization of the ReDCOOL index proved to be more dependable in identifying AD compared to other tests (AUROC 0.729, 95%CI 0.659–0.799; p < 0.001).

The ReDCOOL index appears to increase confidence in the clinical diagnosis of AD compared to each of the visuospatial tests considered. Furthermore, this index is easily calculated and does not prolong the time needed for clinical evaluation, as it does not require a customized patient assessment.

The online version contains supplementary material available at 10.1007/s40520-025-03028-1.