There are many reasons why it's important to seek a doctor's diagnosis as soon as possible. There are many causes for dementia symptoms and this may determine how to treat it. There are even conditions and diseases that can mimic Alzheimer's symptoms that are reversible. (Click here to see the types of dementia) In addition, treatments currently available for Alzheimer's - while limited in their effectiveness and in the number of people they help - have the best chance of working when begun early in the disease. This should become even more so in the future as new treatments are developed that will alter the disease process itself, not just treat the symptoms. Early diagnosis also enables people and families to take immediate action to prepare for worsening symptoms and make appropriate plans for the future.
While there have been significant advances in diagnostic testing methods for Alzheimer’s that use brain scans and spinal taps may detect certain biomarkers of the disease even in its pre-clinical stage, currently, there is no single test that can diagnose Alzheimer's disease with 100% accuracy. Doctors must use a variety of assessments and laboratory measurements to make what we call a “differential diagnosis”. (See "Alzheimer’s Diagnostic Tests” below.) They focus on ruling out all other possible causes for the symptoms. A diagnosis is said to be either possible (not all other causes can be ruled out) or probable (all other causes have been ruled out). Presently, a definitive diagnosis of Alzheimer's is possible only by examining brain tissue after death.