Diagnosis of dementia 3—use of investigations. A survey of current consultant practice, review of the literature and implications for audit

Abstract

SUMMARYThe use of a screening battery of investigations in the assessment of the patient with the dementia syndrome has been recommended by many authorities. A postal survey of hospital specialists showed that the age of the patient influenced their routine use of such batteries. In patients aged < 75 years, their use of investigations closely resembled 'recommended' batteries; patients aged >75 years were much less likely to have a routine screen of investigations. The use of CT scan was much less influenced by the age of the patient. A critical appraisal of the use of investigations in the patient with the dementia syndrome concludes that few of the 'recommended' tests will identify the cause of dementia, but will identify conditions which aggravate cognitive impairment, and that further information on the yield of tests, costs of tests, and the results of treating aggravating factors is urgently needed.KEY woms-Diagnosis, dementia, investigations, audit.Clinical investigations are used in two main ways in the assessment of the patient with the dementia syndrome: to assist in the aetiological diagnosis and to identify aggravating factors such as conditions which are not causative but which by further reducing cognitive function worsen the overall condition of the patient. Investigations may also identify 'risk' factors, such as thyroid disease. Many schemes for the initial screen of investigations have been proposed, but relatively little attention has been paid to their evaluation or to the rationale behind them.We here report the results of a postal survey of clinicians' practice in the diagnosis of dementia, review the literature, and consider the implications for medical audit. METHODThe method has been described in detail elsewhere (Smith et al., 1992). Briefly, a questionnaire, letter and prepaid envelope were sent to 100 consultants in each of four specialities: geriatrics, psychogeriatrics, neurology and general psychiatry. A psychogeriatrician was defined as someone working for the bulk of his or her time as a psychiatrist with special responsibility for elderly patients. These specialities were chosen on the assumption that they are those whose members see the majority of patients presenting to hospital services with the dementia syndrome. Reminder letters were sent out some four weeks after the initial questionnaire; respondents who had died, retired, or left their posts were replaced with 'reserves' from the same specialty. The data sets were closed some eight weeks after the dispatch of the questionnaires. Of the 400 questionnaires despatched, 271 (68%) were completed and returned. Response rates for the four specialities were as follows: geriatric medicine 76%, psychogeriatricians 66%, neurology 66%, psy-

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