What is the role of biomarkers in the workup of Alzheimer disease (AD) in Down syndrome (DS)?

Updated: Nov 13, 2019
  • Author: Norberto Alvarez, MD; Chief Editor: Jasvinder Chawla, MD, MBA  more...
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Biomarkers, physical signs or lab tests consistently associated with a particular disease, are useful for confirming diagnosis, monitoring the disease, evaluating treatment efficacy, and facilitating early intervention to delay disease progression. Unfortunately, at the present time there are no reliable biomarkers useful in diagnosing AD and DS, nor are there good predictors of disease progression or treatment response. However, potential biomarkers have been and continue to be investigated.

Tau protein and beta-amyloid(1-42) (Abeta42) peptide levels in CSF might help differentiate AD from other dementias. Low Abeta42 and high tau protein levels might be associated with a higher risk of AD. [79, 80]

Abeta42, total tau protein, and tau phosphorylated at position threonine 181 (P-tau) levels in CSF have sensitivity and specificity enough to allow identification of AD compared with cognitively normal elderly persons. In addition, these biomarkers can recognize patients with mild cognitive impairment (MCI) who progressed to AD and those who did not. However, performing the lumbar puncture required, which may need to be done several times in order to monitor the improvement of a potential treatment, limited the utility of these markers as front-line screeners.    

Plasma levels of beta-amyloid(1-42) (Abeta42) were found to be higher in persons with DS and dementia than in persons with DS and no AD. [5] Also, higher levels of Abeta42 peptide in nondemented persons with DS were also predictors of dementia and increased mortality. Beta-amyloid 1-40 did not show any correlation. [81] At present, they are not considered to be routinely indicated for the evaluation of persons with DS and potential AD. [80]

Blood biomarkers might be more efficient and cost-effective than CSF biomarkers or radiological tests. However, there are several difficulties in finding the more appropriate ones. [82]

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