Mohammed T. Abou-Saleh

192 PRINCIPLES AND PRACTICE OF GERIATRIC PSYCHIATRYsuch as cerebrovascular disease, would commonly play a part inthis.In the second situation, the assessment is formal and partlyquantitative. A large number of standardized clinical instrumentsand neuropsychological tests for this are now available. They aredescribed in Section DIII of this volume. For the purpose of earlydetection, two points need to be emphasized. Firstly, some of thetests are open to educational or cultural bias, so that they cangenerate false-positive results in some sociodemographic contexts,possibly to the patient’s detriment. Secondly, in this writer’sopinion, many tests are focused on cognitive function, ignoringchanges in behaviour—yet the latter are an important clue to earlydementia. The Psychogeriatric Assessment Scales developed byJorm et al. 8 have gone some way to redress this imbalance (seeChapter 27).LimitationsTo detect dementia early in its course, and to do so with a highlevel of accuracy in different social and educational groups, isnot a straightforward task. The only means currently availableare those clinical instruments described in Section DIII. Thereis no biomedical test with both portability and greater accuracythan these instruments. The clinical instruments all have anumber of limitations. First, the mental status questionnairesare brief, and can act only as screening instruments that sortindividuals into different levels of probability of being a case ofdementia. A questionnaire cannot be expected to do more thanthis. Second, the instrument must be acceptable; yet elderlypeople may dislike extensive cognitive testing, particularly if itshows them up as defective in performance. Third, whether it isa brief questionnaire or a clinical examination, the reliabilityand validity have to be high. The latter means achieving goodlevels of sensitivity and specificity. Fourth, and closely relatedto validity, there is the problem of bias against low intelligenceor poor education. It is highly likely that this causes some falsepositivesto appear in the course of screening.Whatever the method used for early detection, there are threefurther issues to consider. Not all the cases detected willprogress 9,10 and it is hard to predict to whom this will happen.ORGANIC DISORDERSRosenman 11 found very poor predictive validity for five wellestablishedmethods for making this diagnosis. Cooper andBickel 3 argue that there are no good grounds for asking elderlypersons to subject themselves to extensive investigations whensome will undergo no further deterioration. A further impedimentis the cost and service burden from investigating all the possiblecases of dementia generated from a national screening programme.Eastwood and Corbin 12 have argued that the cost wouldbe prohibitive. This is likely to be the case even for the oldersection of the community, where the frequency of secondarydementias is known to be lower than in younger adults. Lastly,there may be unexpected adverse consequences of screening. Thebelief may be false that early detection can contribute toprevention. O’Connor et al. 13 found, unexpectedly, that screeningfor early or mild dementia increased the likelihood of entry intoresidential care.WHAT POSSIBLE SOLUTIONS ARE THERE?Routine screening for dementia at the community level cannotyet be defended. What is required instead is work to evaluateits impact in the manner advocated by Cooper and Bickel 3 .These authors have emphasized the need for research into thefeasibility and effectiveness of early detection as a first steptowards preventive action. They also argue that programmesfor early detection will be successful only if they areincorporated into the work of general practitioners, communitynurses and other health professionals. It is there, and not thetotal community of elderly, where early detection needs first tobe attempted and evaluated to see what benefits, if any, itbrings.At a technical level, it has to be accepted that early detectionof cognitive decline or dementia by brief screening methods hasat least two unavoidable imperfections: first, there will be someerror, whereby the screening test misclassifies a proportion ofindividuals; second, some of this error will be attributable tolow intelligence in the respondent, or educational bias in thetest. Since both of these are likely to produce false-positivesrather than negatives, the problem can usually be overcome bymore detailed clinical assessment and history in a two-phasedesign. In research settings, another desirable strategy in earlydetection is to have a second assessment after an appropriatelapse of time. This is the most certain way to ensure thatdeterioration has indeed taken place, and that it has progressed.Early detection of dementia is currently dependent on clinicalinformation and on cognitive performance related to daily life.Assessment of this is now remarkably satisfactory, although thevalidity of the main clinical instruments has yet to bedemonstrated in community instead of hospital samples.Because dementia has very explicit clinical manifestations andassociated impairments, its early detection is likely to be byclinical means for some time to come. For the present, earlydetection brings no benefit to the elderly in the generalpopulation. But the situation may soon change in the face ofcurrent advances in the molecular biology of Alzheimer’sdisease, where it is conceivable that early detection may becomejustified for genetically high-risk individuals for whom apharmacological intervention could be beneficial 14 . It is fromthese advances that far-reaching consequences for clinicalpractice are now imminent.REFERENCES1. Stewart-Brown S, Farmer A. Screening could seriously damage yourhealth. Br Med J 1997; 314: 533.2. Wilson JMO, Jungner G. Principles and practice of screening.Public Health Papers No. 34. Geneva: World Health Organization,1968.3. Cooper B, Bickel H. Population screening and the early detectionof dementing disorders in old age: a review. Psychol Med 1984;14: 81–95.4. Henderson AS, Huppert F. The problem of mild dementia. PsycholMed 1984; 14: 5–11.5. Brayne C, Day N, Gill C. Methodological Issues in Screening forDementia. Neuroepidemiology 1992; 11: 88–93.6. World Health Organization. The ICD-10 Classification of Mental andBehavioural Disorders. Clinical Descriptions and Diagnostic Guidelines.Geneva: World Health Organization, 1992.7. American Psychiatric Association. Diagnostic and Statistical Manual,4th edn (DSM-IV). Washington, DC: 1994.8. Jorm AF, Mackinnon AJ, Christensen H et al. The PsychogeriatricAssessment Scales (PAS): further data on psychometric properties andvalidity from a longitudinal study of the elderly. Int J GeriatrPsychiatry 1997; 12: 93–100.9. Bergmann K, Kay DWK, Foster MM. A follow-up study of randomlyselected community residents to assess the effects of chronic brainsyndrome and cerebrovascular disease. Psychiatry, Part II. ExcerptaMedica Congress Series 1971; 274: 856–65.