Created: Dec 2021
Screening and Early Diagnosis Methods
Diagnosing dementia often starts with a visit to a nearby doctor after the patient or their family and friends notice some concerning symptoms. The most important sign that such a diagnostic visit is necessary is if the patient’s family is worried about the patient forgetfulness, but the patient themselves is not concerned with it. One drawback of the observational method is that it depends solely on the alertness of the patient or their family. It also does not work well for people who live alone.
Initial screening for dementia is often conducted using MMSE, which stands for Mini-Mental State Examination. It takes a short time (around 15 min) to complete and it assesses cognitive function based on the tests of orientation, attention, memory, language and visual-spatial skills. MMSE result by itself cannot provide a definite diagnosis of dementia. Moreover, it is partially insensitive to mild cognitive impairment and thus often cannot detect mild Alzheimer’s disease. MMSE score can also vary because of demographic factors (e.g. education).
After a visit to the nearby doctor, the patient can be referred to specialized outpatient clinics for further testing, such as detailed neuropsychological tests which include assessment of vision, hearing, speech, potential sleep disorders, mood and thought disturbance and potential depression. The problem is that the number of those tests is large, and no single one can provide an answer whether one has dementia, or if the result might be due to other factors. The fact that several results must be analyzed together before the dementia diagnosis means that the testing takes time, and the results might be difficult to interpret.
A promising new approach to dementia analysis is a simple cognitive function evaluation using eye-gaze detection technology. It is still being developed, and it requires the equipment for tracing eye movement. The biggest issue is the large amount of data generated, which is harder to store than the MMSE test answers, and must be analyzed using a dedicated algorithm.
Structural imaging is also often used in the diagnosis of dementia. Brain MRI is often used for this purpose, as it can detect vascular dementia, and it can provide clues as to which individuals with Mild Cognitive Impairment will develop Alzheimer’s Disease. However, MRI has limited availability in rural areas due to high cost. Also, MRI has limited accuracy in identifying all the patients with Alzheimer’s disease and several other dementia types.
Precision Diagnostics of Dementia
There are some more precise diagnostic methods used to diagnose neuropathologies in the brain.
Positron emission tomography (PET) scans are often used to differentiate between dementia subtypes. In case Alzheimer’s disease is suspected, the doctors will search for the accumulation of amyloid β and tau in the brain using PET. Some studies showed PET to be more accurate in diagnosing Alzheimer’s disease compared to MRI or SPECT. However, the high cost of the ligand tracer and imaging equipment limits the use of amyloidβ/tau PET. Moreover, it can yield false positives if run on cognitively normal older people. Also, its sensitivity and specificity has recently started to be considered insufficient.
One diagnostic method characterized by excellent sensitivity and specificity is the cerebrospinal fluid test, which can be used for very early diagnosis of Alzheimer’s disease. Its main drawback is high invasiveness, as the cerebrospinal fluid must be collected with a needle directly from the patient's spinal cord area.
Tuijl, JP; Scholte, EM; de Craen, AJM; van der Mast, RC (2012). "Screening for cognitive impairment in older general hospital patients: comparison of the six-item cognitive test with the Mini-Mental Status Examination". International Journal of Geriatric Psychiatry. 27 (7): 755–762. doi:10.1002/gps.2776
Mini-Mental State Exam (MMSE) https://www.ncbi.nlm.nih.gov/projects/gap/cgi-bin/GetPdf.cgi?id=phd001525.1
Tomburgh; McIntyre (1992). "The Mini-Mental Status Examination: A comprehensive Review". JAGS. 40 (9): 922–935. doi:10.1111/j.1532-5415.1992.tb01992.x.
Panegyres, P. K., Berry, R., & Burchell, J. (2016). Early Dementia Screening. Diagnostics (Basel, Switzerland), 6(1), 6. https://doi.org/10.3390/diagnostics6010006
Health Quality Ontario (2014). The appropriate use of neuroimaging in the diagnostic work-up of dementia: an evidence-based analysis. Ontario health technology assessment series, 14(1), 1–64.