Diagnostic methods and biomarkers for Alzheimer’s disease

Alzheimer’s disease (AD) is the most frequently occurring and intensively investigated neurodegenerative disorder, which is associated with extracellular senile plaques and intracellular neurofibrillary tangles. In this review, AD related diagnostic strategies and the potential biomarkers of AD will be discussed. Several proteomics methods were developed for disease diagnosis, such as ELISA, MALDI-TOF, SELDI-TOF, and 2 D-electrophoresis. Imaging technologies, such as MRI and PET analyses, are also important, since they could directly show the changes in the brain, associated with dementia progression. MRI technologies might estimate the presence and degree of neurodegeneration by identification and quantification of atrophy. PET could reflect the metabolic changes in the brain by various radioactive molecules (tracers). Along with neuropsycoanalysis of behavioral changes, the progression of dementia can be characterized with biochemical changes in brain metabolisms, in addition to fluctuations in many inflammatory mediators in the cerebral spinal fluid (CSF), blood and in other bodily fluids. These biochemical changes in the brain and other body fluids can be initiated before the appearance of AD symptoms. There is no specific marker for AD along with other dementia, but the combination of different markers may predict the disease progression more accurately. Monitoring the changes in their levels in brain, CSF, blood and body fluids with biomarkers in early disease stages might improve the diagnosis and therapies. Several molecules were established as successful biomarkers for AD diagnosis. Ratio of Abeta42/40 became an important AD marker, which could reflect the disease-associated changes in the blood plasma and CSF. Additional markers were available in blood, such as apolipoprotein E or inflammatory molecules. In CSF, the Abeta42, Tau or phospho-tau could be the most successful biomarker for AD progression. Several new biomarkers and diagnostic approaches were developed for differentiating AD from other forms of dementia. It should be important to predict the AD progression prior to the development of clinical symptoms. Above all, the improvement of above strategies, especially with diverse biomarkers, should support the precise diagnosis of AD, greatly enhancing both AD therapies and preventative measures.