Diagnosis of prodromal and Alzheimer's disease dementia in adults with Down syndrome using neuropsychological tests

Abstract

Introduction We aimed to define prodromal Alzheimer's disease (AD) and AD dementia using normative neuropsychological data in a large population‐based cohort of adults with Down syndrome (DS). Methods Cross‐sectional study. DS participants were classified into asymptomatic, prodromal AD and AD dementia, based on neurologist's judgment blinded to neuropsychological data (Cambridge Cognitive Examination for Older Adults with Down's syndrome [CAMCOG‐DS] and modified Cued Recall Test [mCRT]). We compared the cutoffs derived from the normative data in young adults with DS to those from receiver‐operating characteristic curve (ROC) analysis. Results Diagnostic performance of the CAMCOG‐DS and modified Cued Recall Test (mCRT) in subjects with mild and moderate levels of intellectual disability (ID) was high, both for diagnosing prodromal AD and AD dementia (area under the curve [AUC] 0.73–0.83 and 0.90–1, respectively). The cutoffs derived from the normative data were similar to those derived from the ROC analyses. Discussion Diagnosing prodromal AD and AD dementia in DS with mild and moderate ID using population norms for neuropsychological tests is possible with high diagnostic accuracy.

Screening of Cognitive Changes in Adults with Intellectual Disabilities: A Systematic Review

“…Benejam [18] and as expected, participants with ID with prodromal AD and AD dementia had worse scores than asymptomatic subjects. These authors also recommend cut-off points for the CAMCOG-DS for a diagnosis of prodromal AD and AD dementia in adults with DS, based on population norms stratified by level of ID impairment: mild ID, a score of 80 and moderate ID, scores of 56.…”

“…This inter-test reliability remained after removing MMSE related items in the CAMCOG-DS and excluding participants who achieved zero scores (r=.95). Furthermore, recent research has identified recommended cut-off points for the CAMCOG based on a normative sample of adults with DS[18]. However, it has been noted that this measure may not be suitable for those with severe learning disabilities, severe sensory impairments,…”

Screening of Cognitive Changes in Adults with Intellectual Disabilities: A Systematic Review

“…Although DLD has been used in most studies showing it to be effective in identifying changes over time in people with DS and other ID [ 45 ], one study [ 51 ] revealed that it may not be an appropriate measure to assess dementia in people with severe ID. Recently, DLD was used in Benejam [ 18 ] and as expected, participants with ID with prodromal AD and AD dementia had worse scores than asymptomatic subjects. These authors also recommend cut-off points for the CAMCOG-DS for a diagnosis of prodromal AD and AD dementia in adults with DS, based on population norms stratified by level of ID impairment: mild ID, a score of 80 and moderate ID, scores of 56.…”

“…This inter-test reliability remained after removing MMSE related items in the CAMCOG-DS and excluding participants who achieved zero scores ( r = 0.95). Furthermore, recent research has identified recommended cut-off points for the CAMCOG based on a normative sample of adults with DS [ 18 ]. However, it has been noted that this measure may not be suitable for those with severe learning disabilities, severe sensory impairments, or advanced dementia due to floor effects [ 69 ].…”

“…However, in people with ID, these tests are not appropriate due to pre-existing conditions which makes it difficult to determine baseline cognitive function, meaning the results cannot be interpreted in a substantial and valid way, as there are often no norms for this population [ 11 ]. This has been addressed in recent research carried out by Benejam [ 18 ], who used the CAMCOG-DS in people with Down syndrome to accurately diagnose Alzheimer’s disease. This shows the importance of developing reliable population norms for appropriate instruments when assessing cognitive changes in people with ID.…”