screening investigations in dementia

Last reviewed 08/2023

Investigation of dementia is important primarily to exclude reversible causes of cognitive deterioration:

Perform a midstream urine test if delirium is a possibility.

Blood tests:

  • FBC, ESR, CRP - anaemia, vasculitis
  • T4 and TSH - hypothyroidism
  • biochemical screen - hypercalcium or hypocalcaemia
  • urea and creatinine - renal failure, dialysis dementia
  • glucose
  • B12 and folate - vitamin deficiency dementia
  • clotting and albumin - liver function

Other possible blood tests (though not routinely requested in primary care) include:

  • syphilis serology
  • HIV - if in young person
  • caeruloplasmin - Wilson's disease

Conduct investigations such as chest X-ray or electrocardiogram (ECG) as determined by clinical presentation.

Other possible specialist investigations include:

  • cerebrospinal fluid examination if Creutzfeldt-Jakob disease (CJD) or other forms of rapidly progressive dementia are suspected
  • electroencephalography (EEG) - not routinely indicated
    • consider in:
      • suspected delirium, frontotemporal dementia or CJD
      • associated seizure disorder in those with dementia
  • brain biopsy
    • consider only if a potentially reversible cause is suspected that cannot be diagnosed in any other way
  • imaging
    • use structural imaging to exclude other cerebral pathologies and help establish the subtype of dementia
      • imaging may help to identify treatable causes such as subdural haematoma, normal pressure hydrocephalus, cerebral tumours
      • prefer MRI to assist with early diagnosis and detect subcortical vascular changes. However, CT scanning could be used
      • priority for CT scan should be given to the following
        • atypical presentation
        • rapid unexplained deterioration
        • unexplained focal neurological signs or symptoms
        • history of recent head injury
        • urinary incontinence
        • gait ataxia early in the illness (2)
      • take specialist advice when interpreting scans in people with learning disabilities
    • use perfusion hexamethylpropyleneamine oxime (HMPAO) single-photon emission computed tomography (SPECT) to help differentiate Alzheimer's disease, vascular dementia and frontotemporal dementia
      • the test is not useful in people with Down's syndrome, who may have SPECT abnormalities resembling Alzheimer's disease throughout life
      • if HMPAO SPECT is unavailable, consider 2-[18F]fluoro-2-deoxy-D-glucose positron emission tomography (FDG PET) as an alternative
    • use dopaminergic iodine-123-radiolabelled 2b-carbomethoxy-3b-(4-iodophenyl)-N-(3-fluoropropyl) nortropane (FP-CIT) SPECT to confirm suspected dementia with Lewy bodies (DLB)

Genetic testing – can be offered to patients or to their unaffected relatives if a genetic cause is suspected (1).