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Lookup NU author(s): Dr Gemma Roberts,
Dr George Petrides,
Dr Joseph Kane,
Dr Rory Durcan,
Dr Sarah Lawley,
Professor John-Paul Taylor,
Professor John O'Brien
This is the authors' accepted manuscript of an article that has been published in its final definitive form by Springer Japan KK, 2019.
For re-use rights please refer to the publisher's terms and conditions.
ObjectiveI-123-2β-Carbomethoxy-3β-(4-iodophenyl)-N-(3-fluoropropyl)nortropane (FP-CIT) imaging is anestablished biomarker used in the diagnosis of Lewy body disease. Images are often reportedwith the aid of striatal binding ratios (SBRs), comparing uptake to a normal database via Z scores.It is well-known that SBRs are age-dependent. However, previous studies cover wide age rangesbetween 20 and 80 years, rather than focusing on older adults. Typically a linear relationship isreported, but some authors have suggested that SBRs do not decline as rapidly in old age.Commercial software packages usually adjust the SBR Z score to attempt to compensate for agerelateddecline, but the model used varies. Ensuring age-correction is appropriate for olderadults is important, given that the majority of patients referred for FP-CIT scans are aged over60 years. We examined the relationship of SBR with age in older adults and the effect of agecorrection using research scans from 123 adults over 60 years of age.MethodsTwenty-nine healthy older adults and twenty-three with MCI due to Alzheimer’s disease wereincluded as controls, i.e. individuals with no evidence of Lewy body disease. Their ages rangedfrom 60 - 92 years (mean 76; SD 7.9)). SBRs and Z scores were calculated using BRASS (HermesMedical) and DaTQUANT (GE Healthcare). SBRs were plotted against age and linear mixedeffects models applied. We tested the effect of removing age-correction in BRASS using anindependent dataset of 71 older adults with dementia or mild cognitive impairment.ResultsThe slopes of the linear fits between SBR and age per year were -0.007 (p=0.30) with BRASS and-0.004 (p=0.35) with DaTQUANT. The slopes are smaller than reported in the literature andshow no statistically significant difference from zero.Switching age correction off in BRASS in the test subjects reduced Z scores by approximately 1standard deviation at 80 years of age.ConclusionWe found no statistically significant age-related decline in SBR in adults over 60 years of agewithout Lewy body disease. Commercial software packages that apply a fixed rate of agecorrection may be overcorrecting for age in older adults, which could contribute to misdiagnosis.
Author(s): Roberts G, Lloyd JJ, Petrides GS, Donaghy PC, Kane JPM, Durcan R, Lawley S, Howe K, Sims AJ, Taylor JP, O'Brien JT, Thomas AJ
Publication type: Article
Publication status: Published
Journal: Annals of Nuclear Medicine
Print publication date: 01/06/2019
Online publication date: 21/03/2019
Acceptance date: 15/03/2019
Date deposited: 19/03/2019
ISSN (print): 0914-7187
ISSN (electronic): 1864-6433
Publisher: Springer Japan KK
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