Alzheimer’s disease is confirmed through a clinical diagnosis, in other words, the doctor makes a diagnosis while considering the symptoms, neurological examination and any additional tests available in accordance with current medical standards. At the moment, the most commonly applied diagnostic criteria are version 2 of the International Working Group’s criteria (Dubois, 2014) and those of the US Alzheimer’s Association and National Institute on Aging (2011). Neuropathological confirmation, that is, a study of brain tissue under a microscope, is usually only conducted post-mortem.
Early detection and diagnosis are important so that treatment can be started as soon as possible, and so the patient may be given detailed information in line with their right to independence.
Cognitive tests. Cognitive tests help produce an objective assessment of the patient’s cognitive impairment. They may be short tests (5–15 minutes), known as screening tests, or complete cognitive assessments (30–90 minutes). The patient’s score is compared against the general population of the same age and level of schooling, given that both age and educational level affect the results obtained in these tests. The most popular screening test worldwide is the Mini-Mental State Examination (MMSE).
Blood tests. General health factors that may affect cognitive function are evaluated through blood tests. There are currently no blood tests available that can reliably confirm the diagnosis of Alzheimer’s disease.
Brain neuroimaging. Different types of technology can be used to obtain images of the brain. Computed tomography (CT scan) and magnetic resonance imaging (MRI) provide a life-sized, fixed image of the brain to assess whether there is any significant loss of neurons in the areas typically affected by Alzheimer’s disease or other types of injury. Positron emission tomography (PET) uses substances labelled with a small dose of radioactivity to study neuronal metabolism (glucose PET) or amyloid plaques (amyloid PET).
Cerebrospinal fluid analysis. Cerebrospinal fluid is a liquid that surrounds the brain and spinal cord. As this liquid is in direct contact with the brain it provides an indication of what is occurring inside. Therefore, doctors use it to measure the levels of β-amyloid, tau and phosphorylated tau proteins that accumulate in the patient’s brain. A lumbar puncture is necessary to obtain a sample of cerebrospinal fluid upon which the analysis is performed.
Genetic tests. Genetic tests are only carried out in cases where a genetic form of the disease is suspected.