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

Abstract

Background

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.

Aims

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

Methods

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).

Results

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).

Conclusion

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.