investigations
Last edited 05/2022 and last reviewed 02/2023
There are no specific tests for the diagnosis of Alzheimer's disease. The principle is to rule out the differential diagnoses, and to diagnose Alzheimer's by exclusion.
- FBC – anaemia and infection
- Urea and electrolytes; creatinine; glucose – to rule out diabetes; hyponatraemia – in case of renal failure
- clotting, LFTs – for liver function
- B12, folate – for vitamin deficiency
- TSH, T4 – for myxoedema
- ESR – for vasculitis
- ECG – for arrhythmias
- CXR – for malignancy and infection
- urinanalysis – for sepsis.
Routine electroencephalography (to diagnose CJD) and syphilis serology (VRDL) are probably not indicated unless there are unusual features of presentation.
Other possible investigations include:
- CT/MRI scan – check for tumour, hydrocephalus
- Lumbar puncture in cases of chronic meningitis and TB.
In selected cases further investigations may be indicated:
- angiogram
- jejunal biopsy – to exclude Whipple's disease
- cerebral biopsy
- HIV test
- white cell enzymes
- heavy metal and drug screen.
Note that in Alzheimer's disease there is an early degeneration of the limbic system and the temporo-parietal neocortex. Decreased brain activity in these areas may be detected by positron or single photon emission tomography.
Reference:
total tau or total tau and phosphorylated-tau 181 and Alzheimer's disease
further specialist investigations if Alzheimer's disease suspected