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Screening For Dementia In Primary Care

Clinical Bottom Line
All currently available therapies for dementia rely on early diagnosis of the condition. Although no perfect screening test exists it is imperative that we improve on our current diagnostic rates. The 6CIT probably offers the best compromise between sensitivity, specificity and ease of use.
Never delay referral for memory assessment on the basis that the results are only borderline-positive or where the patient appears to be coping well unaided - These are the group of patients who are likely to benefit most from intervention.

Over the last 30 years numerous tests have been developed for identification of dementia including The Mini Mental State Examination (MMSE)1, The Blessed Information Memory Concentration Scale (BIMC)2, Clock Drawing test, activities of daily living scores (ADL's - eg. Barthel Score) and the Informant Questionnaire on Cognitive decline (IQCODE). Some of these tests have then been further abbreviated to develop other shorter tests such as the 6 item cognitive impairment test (6CIT) a 6 question abbreviation of the BIMC 3, and the Abbreviated mental test score which is a 10 question abbreviation of the mental test score which was originally developed from the BIMC 4

For the purposes of screening in primary care, a test should be short, simple, easy to learn and perform with high sensitivities and specificity's.

The Mini Mental State Examination (MMSE) This was developed by psychiatrists, and is widely regarded as the 'gold standard' test for dementia, see MMSE and Mental State Exam.

Number of questions 30
Time taken to perform 10-15 mins
Score Out of 30, general consensus is that 23 or lower should be treated as positive for dementia.
Advantages Almost global usage, large amount of probability data, can be used to monitor progression of disease
Disadvantages Too lengthy for routine primary care use, inadequate sensitivity in screening population, discriminates in the visually impaired.
Probability Statistics At the 23/24 cut off: Sensitivity = 30-60%, Specificity = 92-100%6, 7
The poor sensitivities above suggest this test is not good at detecting mild or early dementia.

The Abbreviated Mental Test Score Developed by geriatricians, this is probably the best known test in general hospital usage.

Number of questions 10
Time taken to perform 3-5 mins
Score Out of 10, general consensus is that 8 or more is normal and 7 or less significant.
Advantages Simple to perform and score
Disadvantages Very limited validity data, Familiarity has led to numerous adaptations of the questions leading to questionable validity. Culturally specific, Validity has almost certainly deteriorated over the last 30 years as questions such as date of First World War and name of the monarch will carry less significance in the 21st century than they did in the 20th
Probability Statistics At the 7/8 cut off: Sensitivity = 70-80%, Specificity = 71-90%4
These are overall figures (not screening population), No probability data has been found for detection of mild dementia, but correlation data suggests it would be likely to be equivalent to MMSE in a screening group (30-60% sensitivity and 90-96% specificity)

The AMTS lacks validation in primary care and screening populations, most validity data refers to correlation to the MMSE which we already know is a poor screening instrument. It is probably non translatable either linguistically or culturally without revalidation and it is likely that several of the questions will need alteration to bring them up to date. In our ever increasingly multicultural society it is not possible to recommend this test any longer especially in view of its validity data.

The 6 Item Cognitive Impairment Test (6CIT) Developed in 1983 3 by regression analysis of the BIMC, the 6CIT is relatively unknown, though because of use in a large European assessment tool (Easycare©) and recognition by The Royal College of General Practitioners together with new computerised versions its usage is increasing.

6CIT - Kingshill Version 2000 5
1. What year is it? Correct Incorrect
2. What month is it? Correct Incorrect
3. Give the patient an address phrase to remember with 5 components,
eg John, Smith, 42, High St, Bedford
4. About what time is it (within 1 hour) Correct Incorrect
5. Count backwards from 20-1 Correct 1 errorMore than 1 error
6. Say the months of the year in reverse Correct 1 errorMore than 1 error
7. Repeat address phrase Correct 1 error2 errors
3 errors4 errorsAll wrong
/28  

 

Number of questions 6
Time taken to perform 3-4 mins
Score The 6CIT uses an inverse score and questions are weighted to produce a total out of 28. Scores of 0-7 are considered normal and 8 or more significant.
Advantages The test has high sensitivity without compromising specificity even in mild dementia. It is easy to translate linguistically and culturally.
Disadvantages The main disadvantage is in the scoring and weighting of the test, which is initially confusing, however computer models have simplified this greatly.
Probability Statistics At the 7/8 cut off: Overall figures sensitivity 90% specificity 100%,
in mild dementia sensitivity = 78% , specificity = 100%

The 6CIT is a much newer test than the AMT: it would appear to be culturally and linguistically translatable with good probability statistics, however it is held back by it's more complex scoring system. Furthermore it would be nice to see some additional larger population studies using the test.

Investigation Patients identified on screening should be further investigated to exclude reversible causes of memory loss and to try and establish a pattern to the memory loss that might point you towards the cause (see dementia).
Remember depression commonly presents with memory loss as a symptom and thus it would be sensible to screen for this prior to referral.
Depression scores such as the 4 item Geriatric Depression Score are easy and quick to perform with a high sensitivity and specificity. Patients who screen positive for depression should be treated with antidepressants and be reassessed cognitively when their depression has lifted. Care must be taken as dementia and depression often co-exist.

4 Item Geriatric Depression Score
Are you basically satisfied with your life? yes NO
Do you feel that your life is empty? YES no
Are you afraid that something bad is going to happen to you? YES no
Do you feel happy most of the time? yes NO
Score: /4

(Score 1 for answers in capitals: 2-4=Depressed, 1=uncertain, 0=Not depressed)

Routine investigations should also include: Full Blood Count, Erythrocyte Sedimentation Rate, Urea and Electrolytes, Glucose, Liver Function Tests (including gamma Glutamyl Transferase), Thyroid Function Tests, MSU, B12, folate (red cell folate) and VDRL/TPHA.

Consider also doing the following in relevant groups of patients: HIV, Drug Screen, Monitor blood levels of certain drugs (e.g. anticonvulsants or digoxin). Consider blood cultures and CT/MRI scan (to exclude subdural or SOL).

Who To Refer All patients who screen positive should be referred, except where a reversible cause has been identified and subsequent cognitive screening has then been negative (it may be prudent to recall these patients annually for repeat testing).
Most research confirms that early diagnosis is extremely important in order to attempt to arrest progression of the disease. Research confirms that early intervention with measures as simple as patient support and counselling may delay admission to residential care by up to 1 year. This effect is not seen where a delay of as little as 6 months between identification and treatment exists.
Never delay referral for memory assessment on the basis that the results are only borderline-positive or where the patient appears to be coping well unaided - These are the group of patients who are likely to benefit most from intervention.

Where To Refer Patients should ideally be referred to a memory clinic where psychologists will be available to perform detailed cognitive testing to determine whether or not they have a dementia.
Where a memory clinic does not exist the patient should be referred to a Geriatric Psychiatrist with a request for neuro-psychological testing (Neurologists and Geriatricians do not have access to the community mental health teams that are necessary to provide adequate care).

Prognosis What Hope Is There?

  • As already stated counselling may delay time to residential care by up to 1 year in Australian studies.
  • Aspirin and reducing cardiac risks (control of BP, weight, exercise etc..) may prevent further deterioration of vascular type dementias.
  • Oestrogen (HRT) has been shown to delay onset of dementia in women.
  • Non Steroidal Anti Inflammatory Drugs NSAID's may slow progression.
  • Vitamin E and Ginko Biloba may slow progression.
  • Anticholinesterases (Aricept® - donepezil, Exelon®- rivastigmine and soon to launch Galanthamine) have been shown to delay admission to residential care, assist in behavioural difficulty and improve/defer deterioration of cognition.

Screening Currently there is little evidence to support population screening for dementia, but identification of high risk groups may present a better strategy for targeted screening. Consider screening the very elderly (age >75), those with a history of falls/fractured hips; those high attenders or high users of community services, those with known depression, new referrals to the district nurses and PHCT, and non-routine admissions to hospital for elderly.
The MMSE is a well validated test that will always be used to investigate and monitor patients with cognitive impairment6 but is more suitable for hospital usage, its credentials for screening are poor. 7

References

  1. Folstein, M.F., Folstein, S.E., McHugh, P.R. Mini Mental State - a practical guide for grading the cognitive state of patients for the clinician. J Psychiatr Res. 1975 12(3):189-198
  2. Blessed, G., Tomlinson, B.E., Roth, M. The association between quantitative measures of dementia and of senile change in the cerebral grey matter of elderly subjects. British Journal of Psychiatry 1968 114:797-811
  3. Katzman R, et al. Validation of a short Orientation-Memory-Concentration Test of cognitive impairment. Am J Psychiatry 1983 140(6):734-9
  4. Hodkinson, H.M. Evaluation of a mental test score for assessment of mental impairment in the elderly. Age & Ageing 1972 1(4):233-238
  5. Brooke, P., Bullock, R. Validation of The 6 Item Cognitive Impairment Test. Int J Geriatr Psychiatry 1999 14:936-940
  6. Galasko, D., Klauber,M.R., Hofsetter, C.R. The Mini-Mental State Examination in the early diagnosis of Alzheimer's Disease. Arch Neurol 1990 47:49-52
  7. Wind, A.W. et al; Limitations of the Mini-Mental state in diagnosing dementia in general practice. Int J Geriatr Psychiatry 1997 12:101-8

Internet

Article by Dr Patrick Brooke, General Practitioner & Research Assistant in Dementia
e-mail: pbwork@stjohnssurgery.co.uk
Website: www.kingshill-research.org

The Kingshill Research Centre, Swindon, UK owns the copyright to The Kingshill Version 2000 of The 6CIT but allows free usage to health care professionals.

Last issued 08 May 2006









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