Alzheimer disease (AD) is a clinical diagnosis. However, ancillary imaging studies (eg, computed tomography [CT]; magnetic resonance imaging [MRI]; and, in selected cases, single-photon emission CT [SPECT] or positron emission tomography [PET]) and laboratory tests may be used. These tests help exclude other possible causes for dementia (eg, cerebrovascular disease, cobalamin [vitamin B12] deficiency, syphilis, thyroid disease).
Diagnostic criteria established by the National Institute on Aging (NIA) and the Alzheimer’s Association are intended principally to facilitate research. However, the NIA-AA also proposed “core clinical criteria” for diagnosis of mild cognitive impairment (MCI) by health care providers without access to cerebrospinal fluid (CSF) testing or advanced imaging. The NIA-AA criteria for diagnosis of dementia due to AD are clinical, with biomarkers in an assisting, nonessential role.