Objectives With the tools available currently, confirming the diagnosis of inclusion body myositis (IBM) can be difficult. Many patients are initially misdiagnosed with polymyositis (PM). In this observational study at a UK adult neuromuscular centre, we investigated whether amyloid positron emission tomography could differentiate between IBM and PM.
Methods Ten patients with IBM and six with PM underwent clinical review, [18F]florbetapir positron emission tomography and MRI of skeletal musculature. Differences in [18F]florbetapir standardised uptake value ratios in skeletal muscle regions of interest were evaluated. Relationships between [18F]florbetapir standardised uptake value ratios and measures of disease severity (clinical and by MRI of skeletal muscle) were assessed.
Results [18F]florbetapir standardised uptake value ratios were significantly higher in those with IBM compared with PM for all assessed regions (total-[18F]florbetapir standardised uptake value ratio 1.45 (1.28 to 2.05) vs 1.01 (0.80 to 1.22), p=0.005). For total-[18F]florbetapir standardised uptake value ratios≥1.28, sensitivity and specificity for IBM was 80% and 100%, respectively.
Conclusions [18F]florbetapir amyloid positron emission tomography differentiates IBM from PM. Successful development could facilitate accurate diagnosis, inclusion in clinical trials and help avoid unnecessary exposure to potentially harmful treatments.
- inclusion body myositis
- positron emission tomography
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RH and HC contributed equally.
Handling editor Josef S Smolen
Collaborators Sarah Wood, Peter Julyan, David Ashworth, Gerrit van der Vegte, Mike Godfrey, Eleanor Duncan-Rouse, Barry Whitnall, Amy Watkins, Jonathan Harris, Mark Guy.
Contributors JBL and HC had the original idea for the project. JBL applied for funding, obtained ethical approval, designed the study, recruited and assessed subjects, analysed the data and drafted the manuscript. RH assisted with the design of the study, devised the PET scanning protocol and assisted with analysis of the data. RH assisted with the design of the study, devised the MRI scanning protocol and assisted with analysis of the data. MER and HC assisted with patient identification and recruitment. KH was the Administration of Radioactive Substances Advisory Committee (ARSAC) certificate holder. JH assisted with development of the MRI scoring system and scored the MRI scans. All authors contributed to, reviewed and approved the final manuscript.
Funding This work was supported by a grant from the NIHR Manchester Musculoskeletal Biomedical Research Unit (now Biomedical Research Centre), an award from the Centre for Imaging Sciences at the University of Manchester and a grant from the Medical Research Council (MR/N003322/1). This report includes independent research supported by the NIHR Biomedical Research Centre Funding Scheme.
Disclaimer The views expressed in this publication are those of the authors and not necessarily those of the NHS, the National Institute for Health Research or the Department of Health.
Competing interests None declared.
Patient consent for publication Not required.
Provenance and peer review Not commissioned; externally peer reviewed.
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