Diagnostic accuracy of 123I-FP-CIT SPECT in possible dementia with Lewy bodies.

BACKGROUND (123)I-FP-CIT SPECT (single photon emission computed tomography) can help in the differential diagnosis of probable dementia with Lewy bodies (Lewy body dementia) and Alzheimer's disease. AIMS Our aim was to determine the accuracy of (123)I-FP-CIT SPECT in diagnosing people with possible dementia with Lewy bodies. METHOD We undertook a 12-month follow-up of 325 individuals with probable or possible Lewy body or non-Lewy body dementia who had previously undergone (123)I-FP-CIT SPECT. A consensus panel, masked to SPECT findings, established diagnosis at 12 months in 264 people. RESULTS Of 44 people with possible dementia with Lewy bodies at baseline, at follow-up the diagnosis for 19 people was probable dementia with Lewy bodies (43%), in 7 people non-Lewy body dementia (16%) and for 18 individuals it remained possible dementia with Lewy bodies (41%). Of the 19 who at follow-up were diagnosed with probable dementia with Lewy bodies, 12 had abnormal scans at baseline (sensitivity 63%); all 7 individuals with a possible diagnosis who were diagnosed as having Alzheimer's disease at follow-up had normal scans (specificity 100%). CONCLUSIONS Our findings confirm the diagnostic accuracy of (123)I-FP-CIT SPECT in distinguishing Lewy body from non-Lewy body dementia and also suggest a clinically useful role in diagnostically uncertain cases, as an abnormal scan in a person with possible dementia with Lewy bodies is strongly suggestive of dementia with Lewy bodies.