Diagnosing Alzheimer’s disease (AD) early in the pathology is important, not only for the individual’s care but also to identify those who qualify to participate in AD clinical trials. These trials are our best chance of discovering which biomechanisms cause AD and for developing a treatment.
Diagnosing AD is difficult because differentiating between AD, mild cognitive impairment (MCI), and other causes of dementia can be challenging. MCI causes problems with memory and cognition but is not as severe as AD, is most common in those over 65 years of age and does not critically impact daily functioning. An MCI diagnosis is often a precursor to AD, but many people with MCI never develop clinical AD.1 Other dementias, such as frontotemporal dementia, dementia with Lewy bodies, and vascular dementia have unique causes and biological and symptomatic characteristics compared to AD and respond differently to therapeutic interventions. Traditionally, AD is diagnosed by identifying a combination of mental decline, memory loss, and postmortem examination of the brain that reveals the characteristic amyloid beta plaques and neurofibrillary tangles.2 There have been some indications that medicines targeting amyloid plaques can be effective in treating AD, but only when given in the early stages of the disease.
In the last five years, one of the major advances of AD research is the identification of biomarkers associated with AD. Advances in PET scans can now allow detection of amyloid and tau tangles without a postmortem autopsy. Researchers may also use MRIs or cerebrospinal fluid (CSF) tests for confirming a clinical diagnosis of AD.3 Increasingly, researchers are finding associations with inflammation and early stages of AD. It may be that some signs of inflammation in the brain will, in the future, add another indication that a patient may be progressing to the early stages of AD.4
Developing best practices for use of these biomarker tests, and identifying which biomolecules are most associated with AD, is still ongoing. As the use of diagnostic testing is refined, it may contribute greatly to the advancement of AD clinical trials and eventually be used in everyday clinical practices. With these advances, correctly diagnosing AD in its earlier stages becomes possible and the world takes a step closer to discovering an effective medical treatment.