Validation of Blood Biomarkers for Alzheimer's Disease

Alzheimer's disease (AD) has gradually become one of the major global public health issues due to its prevalence, which increases with age and life expectancy, and the economic cost of caring for patients whose cognitive decline progressively leads to loss of functional autonomy. The diagnosis of AD is based on a multidisciplinary approach, involving, among other things, evaluation of the medical history together with clinical symptoms and signs, neuropsychological tests and neuroimaging. The quantification of cerebrospinal fluid (CSF) core biomarkers (amyloid beta peptides \[Ab1-40 and Ab1-42\], total tau \[t-tau\] and its phosphorylated form on threonine 181 \[p-tau(181)\]) has progressively proven utility for the diagnosis of AD and its prodromal forms. CSF biomarkers are now included in international guidelines for the diagnosis of AD in research settings and clinical practice and the Alzheimer's Association appropriate use criteria for the use of lumbar puncture and CSF testing in the diagnosis of AD have been published. Such biochemical diagnostics are currently implemented in many specialized centers around the world. Recent progress in the biological diagnosis of AD is considerable, with the possibility, thanks to ultra-sensitive tests realized notably with the SIMOA technology, of having Ab1-40, Ab1-42, t-tau and p-tau(181) also detectable in the blood using commercial kits. The performance for AD detection has been evaluated by many groups including on retrospective samples. It is now essential to evaluate the interest of blood-based biomarkers of AD, prospectively and in real life condition to confront them with pre-analytical and analytical variabilities. It is also important to position them in relation to CSF analysis and AD management, from risk assessment, diagnosis, to therapeutic strategies.