Tests used in dementia research
Participating in research
Once the study is underway, participants will be expected to comply with the researchers’ requests (e.g. to take a particular tablet at a set time, to undergo batteries of tests, to fill out questionnaires, to be observed, to try out a new form of assisted technology etc.) for the duration of the study. However, participants are under no legal obligation whatsoever to do so and can withdraw from the study at any time (please see section on ethical issues).
For people taking part in clinical trials, cognitive tests, as well as tests to measure the ability to carry out daily tasks, are quite common. This is because at some point in the process of developing new drugs, the researchers have to be able to show by means of a validated assessment scale that the drug improves cognitive and global functioning. In other studies too, researchers may need to measure the cognitive and physical abilities of participants or to determine how they have been affected by particular interventions or factors.
In this section, details are provided of some of the tests most commonly used in studies and in connection with clinical trials.
Alzheimer’s Disease Assessment Scale (ADAS) and Al zheimer’s Disease Assessment Scale - Cognition (ADAS-Cog)
The Alzheimer’s Disease Assessment Scale (ADAS) is a two part scale designed to assess cognitive and non-cognitive symptoms of Alzheimer’s disease. It is one of the most frequently used scales in clinical trials but is quite time-consuming (taking on average 45 minutes to complete).
The part which measures cognitive faculties is known as the ADAS-Cog. There are 7 performance items and 4 clinician-rated items coving memory, orientation, language and praxis. Possible scores range from 70 (severe impairment) to 0 (no impairment). The part which measures non-cognition contains 10 clinician-rated items covering agitation, depressed mood, psychosis (delusions and hallucinations), attention/concentration and changes in weight. It is not generally used for the assessment of people with severe dementia (need to check this).
The Mini-Mental State Examination (MMSE)
The Mini-Mental State Examination (MMSE) is a measure of cognitive function which was originally designed as a screening tool. It is perhaps the most widely used measure of cognitive function in the world and it is also used by researchers. It consists of 11 items designed to evaluate orientation, memory, attention, language and motor skills. Possible scores range from 30 (severe impairment) to 0 (no impairment). People with Alzheimer’s disease not receiving treatment tend to decline 2 to 4 points per year on the MMSE (Schneider, 2001). However, the MMSE is less sensitive to progressive decline in people who already have very low scores. A cut-off score of 23 for the presence of cognitive impairment has been suggested although this may vary slightly depending on the patient’s level of education (Burns et al., 2002). The MMSE is easy to administer and only takes about 5 to 10 minutes to complete.
Activities of Daily Living Scale (ADL)
The Activities of Daily Living Scale (ADL) was developed by Katz in 1963. It is used to assess the level of a person’s physical functioning and is generally considered an accurate measure. A person’s ability to accomplish a range of tasks without assistance is evaluated. The six basic activities are: 1. bathing, 2. dressing, 3. toileting, 4. transferring (i.e. getting in and out of bed or a chair), 5. continence and 6. feeding. Whilst they are very practical tasks, they all require a certain degree of cognitive functioning as tasks need to be planned, things organised, objects recognised and correctly used and choices made etc.
Instrumental Activities of Daily Living Scale (IADL)
In 1969, Lawton and Brody designed the Instrumental Activities of Daily Living (IADL) Scale which was aimed at evaluating more complex activities of daily life. The patient’s capacity or incapacity to accomplish various tasks provides evaluators with a kind of proxy measure of that person’s cognitive abilities. Whilst the tasks seem very practical, they require a higher degree of cognitive functioning than those covered by the ADL scale. There are divided into eight categories: 1. ability to use the telephone, 2. shopping, 3. preparing food, 4. housekeeping, 5. laundry, 6. transportation, 7. managing own medication and 8. ability to handle finances.
Within in each section, there are various activities for which points are attributed. For example, in the section on transportation a point is given for each of the following: travels independently on public transportation or drives own car; arranges own travel via taxi, but does not otherwise use public transportation; travels on public transportation when accompanied by another; but no points are gained for: travel limited to taxi or automobile with assistance of another; does not travel at all.
Disability Assessment for Dementia (DAD)
The Disability Assessment for Dementia (DAD) scale is designed to measure functional abilities related to basic and instrumental activities of daily living. It contains 40 items and takes about 20 minutes to complete.
Neuropsychiatric Inventory (NPI)
The Neuropsychiatric Inventory (NPI) is a short test which is used to assess behavioural and neuropsychological disturbances in people with dementia. It measures a range of symptoms including delusions, hallucinations, dysphoria , anxiety, agitation/aggression, euphoria, disinhibition, aberrant motor activity, apathy, irritability, night-time behavioural disturbances and eating disturbances. The severity and frequency of symptoms are measured separately.
Quality of Life in Alzheimer’s Disease Patient and Caregiver Report (QoL-AD)
The Quality of Life in Alzheimer’s Disease Patient and Caregiver Report (QoL-AD) is used to assess quality of life and is based on reports provided by people with Alzheimer’s disease and their carers. The scale contains 13 items, each marked on a 4 point scale. The areas covered are mood, physical health, memory, relationships, self-esteem and current situation.
Clinical Dementia Rating (CDR)
The Clinical Dementia Rating (CDR) is a global measure of dementia, which is usually completed by a clinician by means of an interview with the patient and the carer (which takes about 40 minutes). The clinician may already have gathered much of the information in the course of his/her previous contact with the patient.
The CDR provides a means to categorise people with dementia according to stages. A score of 0 would indicate no dementia and 0.5, questionable dementia, whereas a score of 1, 2 or 3 would be an indication of mild, moderate or severe dementia (Burns et al., 2002). Six areas are covered i.e. memory, orientation, judgement and problem-solving, community affairs, home and hobbies, and personal care.
Computerised Axial Tomography (often abbreviated to CT scan or CAT scan) is a type of scanning which allows researchers to detect shrinkage of the brain (which can also occur in people who do not have dementia). It can also serve to help differentiate between vascular dementia and Alzheimer’s disease. The scanning process involves taking pictures of slices of the brain by means of X-rays and a computer. A harmless dye may be injected to make the images clearer. The scanning takes about 15 to 30 minutes and is not painful or disturbing (i.e. no loud noises). However, the person needs to remain still during the process. For this reason, if a person is slightly agitated, he/she may be given a light sedative. (Source: Royal College of Psychiatrists, 2009).
Magnetic Resonance Imaging (MRI) is another type of scanning which takes pictures of the brain but not using X-rays. It provides more detail than CT scans and is also more expensive. MRI detects radio signals in the body which are produced in response to the effects of a powerful magnet contained in the scanner. The scanner is very noisy and whilst the whole process is painless, it may take up to an hour. It can be fairly uncomfortable to remain completely still for so long.
Single Photon Emission Computerised Tomography (SPECT) is a scan which measures blood flow in the brain. The patient is given an injection of a very mild, harmless radioactive substance (radionuclide) which travels in the blood to the brain. The pictures from the scan show slices of the brain and indicate the extent to which different parts of the brain have taken up the injected substance. This serves as a measure of how effectively blood is reaching different parts of the brain. The person has to sit still during the scanning procedure, which takes about XX minutes.
Positron emission tomography (PET) produces a three dimensional picture of functional processes within the body (e.g. blood flow, oxygen use or glucose metabolism) using radionuclide as a tracer. The images obtained are usually reconstructed by means of a CT X-ray scan which is performed at the same time as the PET scan. The PET scan may use fluorodeoxyglucose (FDG) in order to measure regional glucose uptake. The tracer may be injected, swallowed or inhaled. After receiving it, the person may have to wait for about 30 to 60 minutes whilst the tracer travels through the body before the actual scanning (which takes 20 to 30 minutes) takes place (Source: Wikipedia, 2009 and www.radiologyinfo.org , 2009).
Last Updated: vendredi 21 août 2009