Biomarkers are biological indicators that are used to find out if a person has the disease or in what phase it is. An example of biomarkers known is insulin, having a high level is an indicator of diabetes.
The information that is extracted from biomarkers is essential to fine-tune the diagnosis in cases where neuropsychological tests and the usual neuroimaging tests (eg scanner or resonance) can not be clarified with sufficient degree of certainty.
In Alzheimer's disease, the most studied biomarkers are those that are determined by the cerebrospinal fluid (LCR), a liquid that breaks the brain. The biomarkers in this liquid are the β-amyloid peptide42, the tau-total protein (t-tau) and the tau-phosphorylated (p-tau) protein.
These biomarkers measure both cerebral amyloidosis (β-amyloid42) and neurodegeneration (t-tau and p-tau). Both biomarkers help to increase diagnostic certainty in patients with mild cognitive impairment (DCL) and Alzheimer's disease according to the new diagnostic criteria (Alberts et al., 2011; McKhann et al., 2011).
In the Foundation, the biomarkers are determined in our laboratory by the technique of ELISA that is the most used. Our laboratory participates in the external quality control program of the Alzheimer's Association LCR (AA) (Mattsson N et al., 2013) biomarkers.
For the interpretation of the results of the analysis of biomarkers, the cutting points of each biomarker that is established in the laboratory are used and its value is the one used to indicate whether the biomarker is altered or not. If the three biomarkers are altered, it is considered that biomarkers are compatible with Alzheimer's disease and, if the three biomarkers are normal, it means that there is no Alzheimer's disease.