Dementia workup. Deciding on laboratory testing for the elderly.

OBJECTIVE: To review Canadian Consensus Conference on the Assessment of Dementia (CCCAD) guidelines for laboratory evaluation of dementia, and to make recommendations to family physicians based on these guidelines and other literature. DATA SOURCES: English-language data sources from 1992 to March 1997 were searched on MEDLINE using the MeSH headings dementia, dementia/diagnosis, and cognition. Key words relating to specific laboratory tests or conditions, such as neurosyphilis or vitamin B12, were also used. STUDY SELECTION: Original research articles using prospective and retrospective methods were accepted. Articles reviewing the general investigation of potentially reversible dementia were included, as were articles looking at the sensitivity, specificity, and utility of investigations for specific conditions causing dementia. SYNTHESIS: Family physicians are not always aware of CCCAD recommendations for the investigation of dementia. There was C-level evidence for use of CCCAD core investigations (complete blood count and electrolyte, glucose, calcium, and thyroid levels) and for tests to be done "when the clinical situation warrants" (B12 levels, computed tomography scan of the head, and testing for syphilis).
CONCLUSIONS: The CCCAD guidelines were supported by most literature on the workup of dementia. Prospective cohort studies suggest use of clinical judgment in ordering laboratory investigations. No controlled trials were available, and most recommendations arose from consensus rather than from research evidence. The prevalence of reversible dementias is likely lower than previously believed, which further supports a selective approach to investigations. Identification of reversible causes and exacerbating factors is still the goal.