Treatable, or at least modifiable factors which may affect the intellect may be discovered. Underactive thyroid, vitamin, nutritional deficiencies, neurosyphilis, series of small strokes, etc. Potentially harmful medicines can be eliminated. Currently there is no foolproof test which identifies a person who is about to begin intellectual deterioration which will lead to Alzheimer's Disease. Generally, it takes four years from the appearance of the very earliest symptoms to definitive diagnosis.
Diagnosis is accomplished primarily through examination, with laboratory tests having a lesser role.
Memory testing is commonly done, along with some basic blood tests and often a brain scan. More complicated tests, such as spinal fluid tests or complex brain scans, are done rarely, usually in exceptional or questionable cases. Certain genetic tests, such as the ApoE test, may indicate increased predisposition to the disease. However, because it does not prove the existence of the disease, it is not a standard part of the diagnostic testing. Despite the delay in early diagnosis of Alzheimer's disease, there are some advantages to early treatment.