IC‐P1‐041: Predictive diagnostic accuracy of 123I‐FP‐CIT SPECT in possible dementia with Lewy bodies: A 12‐month follow‐up study

123I-FP-CIT SPECT can help in the discrimination of probable dementia with Lewy bodies (DLB) from Alzheimer's disease (AD). However, its usefulness in more clinically uncertain “possible DLB” cases is unknown. The main aim of this study was to determine the diagnostic accuracy of 123I-FP-CIT SPECT in possible DLB cases, validated by final clinical diagnosis twelve months later. We undertook a twelve month follow-up of 325 subjects with probable or possible DLB or non-DLB dementia who had previously undergone 123I-FP-CIT SPECT as part of phase III multicentre study. A consensus panel established diagnosis at 12 months in 264 cases, blind to SPECT findings. In the overall study, SPECT scans had a mean sensitivity of 78% for detecting probable DLB, with a specificity of 93% for excluding non-DLB dementia. 44 possible DLB cases were followed-up, of whom 19 (43%) became probable DLB cases, 7 (16%) non-DLB and 18 (41%) remained possible cases. Of the 19 who became probable DLB, 12 had abnormal scans, while all 7 cases who became non-DLB had normal scans (sensitivity 63%, specificity 100%, positive predictive value 100%). Our findings suggest an important and clinically useful role 123I-FP-CIT SPECT in diagnostically more uncertain DLB cases, as an abnormal scan in a possible DLB subject is highly suggestive of future development of probable DLB.