THE STICK DESIGN TEST (SDT): CAN A VISUOCONSTRUCTION TEST HELP DISCRIMINATE HEALTHY CONTROLS (HC), MILD COGNITIVE IMPAIRMENT (MCI) AND ALZHEIMER’S DISEASE (AD)?

Abstract

Cognitive assessment is essential for an accurate diagnosis of HC, MCI and AD. Many brief tests exploring visuoconstructional abilities have been proposed as practical alternatives to otherwise extensive neuropsychological (NPS) testing1,2,3. The SDT is proposed to be a simple, nongraphomotor, visuoconstructional test, with little dependence from educational levels4. The present study aims to analyze the discriminative power of the SDT in a sample of HC, MCI and AD. Sixty-eight individuals, aged 60 years and older, selected from University of São Paulo's dementia center were evaluated through a NPS composite constituted by MMSE, Brief Cognitive Screening Battery (BCSB), phonemic fluency (PF) and visuospatial parameters (VSP) - the clock drawing test (CDT), the cube and intersecting infinity loops (IIL) copies. NPS assessment was performed to determine the diagnosis of MCI and AD according to international criteria5,6, while HC were classified if screening tests and clinical characteristics were normal. AD patients were older than HC and MCI participants and less educated than the HC group (table 1). In the NPS tests, AD group showed poorer performance than the HC and MCI groups, as expected (table 2). The scores obtained in the construction step of the SDT appeared to show a ceiling effect, especially if we take into consideration the cut-off values (11.5), too close to maximum points possibly acquired (12) at this phase (table 3). Most importantly, the delayed recall step demonstrated good accuracy (cut-off = 4,5; AUC = 0,835) (table 4). However, SDT was not able to differentiate HC from MCI's (AUC = 0,542) in this sample (figure 1). Furthermore, the SDT showed positive correlations with VSP tests, albeit considered weak to moderate values (table 5). Our findings are in line with the literature4,7, demonstrating that the SDT is a useful visuospatial resource for screening patients for AD diagnosis, but not sensible to distinguish MCI from HC in highly educated individuals. ROC Curves. Note. HC = Healthy controls; MCI = Mild cognitive impairment; AD = Alzheimer's disease.