Diagnosing dementia is a complex and difficult process. There is no one test that can tell if someone does or does not have Alzheimer's disease or another dementia. One of the tests your doctor will use is a mental status test. Various forms of this test exist, but the important point is that the doctor administers and evaluates the test using skill, knowledge and experience. This is different from memory screening tests, which are done in the community without professional analysis.

Memory screening done in the community (or “population-based memory screening”), usually involves giving someone a simple mental status test. After the test, the result is a number that shows if someone may have memory problems.

Often these brief mental tests result in "false positives" and "false negatives." A "false positive" is when a person who doesn’t have Alzheimer’s disease or other dementia still fails or scores poorly on the test. A "false negative" happens when person who does have Alzheimer’s disease or other dementia "passes" or scores well on the test.

It takes time and expertise to diagnosis dementia, because the doctors first have to rule out other possible causes, such as depression, thyroid or heart disease, infections, drug reactions or alcohol abuse.

• People who are experiencing memory issues accompanied by difficulties in day-to-day activities and skills should contact their health-care provider.

• Alzheimer’s disease and other dementias are complex diseases of the brain and qualified health care providers should be involved in diagnosing these conditions.

• Online self-assessments of cognitive health are possibly useful for the screening of Alzheimer’s disease and other dementias and may pose risks to users unless completed following the advice of a health provider to do so.

• Scientists have raised ethical concerns with most online self-assessments for the diagnosis or screening of Alzheimer’s disease and other dementias, such as potential issues around the privacy and confidentiality of the information collected.

• The Alzheimer Society provides information, education and support to help people with dementia and their families live as well as possible.