A neurological examination may be performed to assess for signs of neurological dysfunction, such as abnormal reflexes, muscle weakness, or coordination problems. Imaging tests such as magnetic resonance imaging (MRI) or positron emission tomography (PET) scans may be used to rule out other possible causes of cognitive impairment, such as stroke, tumor, or hydrocephalus. These imaging studies can also help visualize changes in the brain associated with AD, such as atrophy (shrinkage) of brain regions involved in memory and cognition or the presence of β-amyloid plaques and tau tangles. Blood tests may be performed to rule out other medical conditions that can cause cognitive impairment, such as thyroid dysfunction, vitamin deficiencies, or infections. Cerebrospinal fluid (CSF) analysis may be considered in some cases to measure levels of β-amyloid and tau proteins, which can be indicative of AD pathology. In addition, non-invasive diagnostic tests are being considered as a part to the comprehensive AD assessment. One such test, PrecivityAD2 is a clinical care assay that measures both plasma amyloid beta and tau peptide concentrations. Other assays utilizing not only blood, but saliva and urine are currently being researched. Diagnosis of AD is typically based on clinical criteria established by organizations such as the National Institute on Aging and the Alzheimer's Association (NIA-AA) or the International Working Group (IWG) for AD. These criteria consider the presence and pattern of cognitive symptoms, the progression of symptoms over time, and the exclusion of other possible causes of dementia.