Screening for cognitive impairment

Things to consider when screening for cognitive impairment

Screening for dementia is not recommended for the general population. However, healthcare professionals should be aware of clinical features that may suggest cognitive impairment and should also be aware of the risk factors of dementia in people with conditions such as Down's syndrome and other learning disabilities, after a stroke and in Parkinson's disease¹ . General practitioners need to be able to recognise cognitive impairment and possible dementia using:

• History taking.

• Cognitive and mental state examination.

• Physical examination and other appropriate investigations.

• A review of medication in order to identify and minimise use of drugs, including over-the-counter products, which may adversely affect cognitive functioning.

See the separate Dementia and Supporting the Family of People with Dementia articles.

The rest of this article deals with the screening tests that can be used to detect cognitive impairment. The limitation of such cognitive function tests should be recognised and one UK study found that increased use of the tests was not reflected in an increase in the hospital diagnosis of dementia² .

Screening tests for cognitive impairment can adequately detect dementia but there is no strong evidence whether interventions for patients or their carers have a clinically significant effect for people with cognitive impairment detected earlier³ . However, early diagnosis allows the person to plan ahead while they still have the capacity to make decisions about their future care, enables the person and their family members to receive timely practical information, advice and support, and allows access to available drug and non-drug treatments which may improve cognition, improve quality of daily life and delay institutionalisation¹ .

Clinical assessment for cognitive impairment

• Clinical cognitive function tests in those with suspected dementia should include examination of attention and concentration, orientation, short-term and long-term memory, praxis, language and executive function.

• As part of this assessment, formal cognitive testing should be undertaken using a standardised instrument. For the purposes of screening in primary care, a test should be short, simple and easy to learn, and perform with high sensitivities and specificities.

• Those interpreting the scores of such tests should take full account of other factors known to affect performance, including educational level, skills, previous level of functioning and attainment, language and any sensory impairments, psychiatric illness or physical/neurological problems.

• Formal neuropsychological testing should form part of the assessment in cases of mild or questionable dementia. Many of the standard cognitive tests are designed for measuring impairment in older adults of average ability, whose cognitive abilities are generally slightly different in range and strength from those under 65 years. In the case of younger (or highly able older) people, a review by a specialist Cognitive Neurology team or a Clinical Neuropsychologist is recommended, as they have the tools to make diagnoses that are very frequently missed by the standard test protocols.

• At the time of diagnosis of dementia and at regular intervals subsequently, assessment should be made for medical comorbidities and key psychiatric features associated with dementia, including depression and psychosis, to ensure optimal management of co-existing conditions.

The General Practitioner Assessment of Cognition (GPCOG)

The GPCOG consists of cognitive function test items in addition to historical questions asked of an informant. It has been considered to be reliable and superior to the Abbreviated Mental Test (AMT) and to the Mini Mental State Examination (MMSE), in detecting dementia^{4 5} . However, the research on which this opinion is based was conducted some time ago, and the results of a more up-to-date systematic review are awaited

The Mini Mental State Examination

The MMSE was developed by psychiatrists and is highly regarded^{6 7} . It has some methodological issues and may discriminate positively for those with a higher level of educational attainment. There is no strong evidence to support the use of MMSE as a stand-alone test for the identification of patients with mild cognitive impairment (MCI) who may develop dementia⁸ .

The Six-item Cognitive Impairment Test (6CIT)

Developed in 1983, the 6CIT is relatively unknown, although because of recognition by The Royal College of General Practitioners together with new computerised versions, its usage is increasing.

The 6CIT is a much newer cognitive function test than the AMT (see 'Abbreviated Mental Test (AMT)', below) and it would appear to be culturally and linguistically translatable with good probability statistics; however, it is held back by its more complex scoring system. One study reported that it excluded dementia accurately in an older Emergency Department population⁹ . The National Institute for Health and Care Excellence (NICE) recommends it as one of the validated tests for use in a non-specialist setting¹⁰ .

Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE)

When combined with cognitive tests, such as the MMSE, the IQCODE provides a useful overview, and hence sensitivity and specificity as a screening test can be improved¹¹ .

The questionnaire asks how the patient compares today with ten years ago in various activities - eg, remembering birthdays and recalling conversations.

Abbreviated Mental Test (AMT)

The AMT is a quick-to-use screening test that was first introduced in 1972 but is less widely used today. Developed by geriatricians, this is probably the best-known test in general hospital usage; however, it lacks validation in primary care and screening populations.

Its disadvantages are the ability to be confounded by intelligence, age, social class, sensitivity of hearing and history of stroke. A four-point AMT has been developed which should be easier to administer than the original ten-point version and may obviate some of these problems¹² .

Test Your Memory (TYM) Test¹³

This is a useful cognitive function test, particularly where clinician time is limited. It is advocated by NICE as a validated test suitable to be used in a non-specialist setting¹⁰ . The test involves:

• Orientation.

• Ability to copy a sentence.

• Semantic knowledge.

• Calculation.

• Verbal fluency.

• Similarities.

• Naming.

• Visuospatial abilities.

• Recall of a copied sentence.

The ability to do the test is also scored.

Other tests recommended by NICE^{10 1}

These include:

The 10-point cognitive screener (10-CS)

• The 10-CS involves three temporal orientation questions (year, month, date), a three-word recall, and a four-point scaled animal naming task.

• One point is scored for each of the temporal questions and each word recalled, and the scores for the animal naming task range from 0 points for 0-5 animals, to four points for 15 or more animals.

• A score of eight or more is normal, 6-7 suggests possible cognitive impairment, and 0-5 suggests probable cognitive impairment.

6-item Screener

• This is comprised of three temporal orientation questions (year, month, day of the week) and a three-word recall.

• Each correct response scores one point for a total maximum of six points.

• Two or more errors are considered high risk for cognitive impairment.

Memory Impairment Screen (MIS)

• At the beginning of the assessment the person is shown four words. The person is then given a category and requested to identify which word fits into that category. This is completed for all four words and it is explained that they will be asked to remember the words in a few minutes. A distractor activity is performed for two or three minutes (for example, counting to 20 and back, counting back from 100 by 7, spelling the word 'world' backwards) and then the person is asked to recall the four words.

• The maximum score is 8 (two points for each word recalled without prompting and one point for each word that requires prompting). A score of 5-8 indicates no cognitive impairment, and a score of 4 or less indicates possible cognitive impairment.

Mini-Cog Test

• This consists of two components: a three-item recall test for memory and a clock drawing test.

• There is one point for each word remembered after the clock has been drawn, and two points for a normal clock.

• A total score of 3, 4, or 5 indicates lower likelihood of dementia but does not rule out some degree of cognitive impairment.