Declaration of interest
M.F. reports grants from National Institute for Health Research, K.H. reports grants and personal fees from Lilly/Avid Radiopharmacuticals, personal fees from GE Healthcare, Cytox and Elan, other from Herholz Consulting GmbH, J.O.B. reports grants and other from GE Healthcare, grants and other from Lilly, other from Bayer Healthcare, other from TauRx, other from Cytox.
Imaging biomarkers for Alzheimer's disease include medial temporal lobe atrophy (MTLA) depicted on computed tomography (CT) or magnetic resonance imaging (MRI) and patterns of reduced metabolism on fluorodeoxyglucose positron emission tomography (FDG-PET).
To investigate whether MTLA on head CT predicts the diagnostic usefulness of an additional FDG-PET scan.
Participants had a clinical diagnosis of Alzheimer's disease (n = 37) or dementia with Lewy bodies (DLB; n = 30) or were similarly aged controls (n = 30). We visually rated MTLA on coronally reconstructed CT scans and, separately and blind to CT ratings, abnormal appearances on FDG-PET scans.
Using a pre-defined cut-off of MTLA ⩾5 on the Scheltens (0–8) scale, 0/30 controls, 6/30 DLB and 23/30 Alzheimer's disease had marked MTLA. FDG-PET performed well for diagnosing Alzheimer's disease v. DLB in the low-MTLA group (sensitivity/specificity of 71%/79%), but in the high-MTLA group diagnostic performance of FDG-PET was not better than chance.
In the presence of a high degree of MTLA, the most likely diagnosis is Alzheimer's disease, and an FDG-PET scan will probably not provide significant diagnostic information. However, in cases without MTLA, if the diagnosis is unclear, an FDG-PET scan may provide additional clinically useful diagnostic information.
Funded by the National Institute for Health Research, NIHR Biomedical Research Centre and Lewy-body Dementia Biomedical Research Unit awarded to Newcastle upon Tyne Hospitals NHS Foundation Trust and Newcastle University, and the NIHR Biomedical Research Centre and Biomedical Research Unit in Dementia awarded to the Cambridge University Hospitals NHS Foundation Trust and the University of Cambridge.
- © The Royal College of Psychiatrists 2015.
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