Labs: Lab tests are used to identify any potential reversible or modifiable contributors to dementia.​ The yield for identifying a reversible/modifiable cause of dementia on bloodwork is low.

• Many guidelines/experts recommend checking at least B12 and TSH. Variability exists in obtaining other lab tests including CBC, CMP, HIV, and syphilis testing. ​We recommend at least checking CBC, CMP, TSH, and B12/folate.
  • AAN practice parameter (in process of being updated):
    • “B₁₂ deficiency is common in the elderly, and B₁₂ levels should be included in routine assessments of the elderly (Guideline).”
    • “Because of its frequency, hypothyroidism should be screened for in elderly patients (Guideline).”
  • AAFP evaluation for dementia: “The standard laboratory evaluation for patients with cognitive impairment includes testing for anemia, hypothyroidism, vitamin B₁₂ deficiency, diabetes mellitus, and liver and kidney disease.”​
    
• Advanced diagnostic testing: While not yet included in the routine evaluation of dementia, a lumbar puncture +/- blood test to collect CSF biomarkers for Alzheimer’s pathology are performed in research settings and by some clinicians.
  • The PrecivityAD test is the only commercially-available blood test that can be ordered by clinicians, although it is not covered by insurance at this time. This test measures two amyloid-beta peptides as well as apolipoprotein E and generates a score, using these measurements and a patient’s age, to give a score indicating the probability of finding amyloid plaques on a PET scan. Primary care providers should be aware that this test exists, but we do not expect most PCPs to feel comfortable ordering this test themselves.
  • CSF biomarkers that are collected during lumbar punctures may include amyloid-beta, total tau, and phosphorylated tau. At this point, CSF testing should only be ordered by dementia experts.
    • To read more about circumstances in which dementia experts may order CSF testing: Appropriate use criteria for CSF biomarker testing for Alzheimer’s, as developed by an Alzheimer’s Association-sponsored workgroup
  • AAN recommendation (for MCI): “For interested patients, clinicians may discuss the option of biomarker research or refer patients or both, if feasible, to centers or organizations that can connect patients to this research (e.g., subspecialty centers, Trial Match, ClinicalTrials.gov) (Level C).”​
    
• A note on genetic testing: Testing for genes linked to Alzheimer’s, such as APP, PSEN1 and PSEN2, should only be ordered by experts, in specific scenarios, and with consideration of genetic counselling​.

Imaging: Generally, imaging is used to rule out the presence of non-dementia related pathology.​

• MRI brain without contrast is recommended in most situations​
  • American Academy of Neurology: Recommends MRI brain without contrast (or CT brain without contrast if MRI cannot be obtained)​
  • At some institutions, specialized MRI brain protocols are available to assess for hippocampal atrophy​
  • National Institute for Health and Care Excellence in England: Recommends offering imaging unless “dementia is well established and the subtype is clear”​
• Note on PET scans: Specialized types of PET scans, like the amyloid PET scan, are mostly used in research settings and are not routinely ordered in evaluations. Some dementia experts may order PET scans, but we do not recommend that PCPs order them.
  • To read more about circumstances in which dementia experts may order a PET scan: Appropriate use criteria for PET scans

• Consider referral for neuropsychiatric testing if:
  • The evaluation reveals a borderline diagnosis
  • The cognitive testing does not match the history
  • The family and/or patient request it