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Imaging of sacroiliac joints (SIJ) is one of the cornerstones in early recognition of axial spondyloarthritis (axSpA).1 Currently, MRI is the preferred technique to visualise bone marrow oedema (BME), which can be defined as sacroiliitis when certain criteria are met.2 However, the definition of sacroiliitis as being ‘highly suggestive for axSpA’ has limitations in situations when BME is subtle or when SpA-like BME lesions are present due to other conditions such as mechanical stress.3 4 This underscores the need for additional and more specific imaging modalities. Given the marked efficacy of tumour necrosis factor (TNF) inhibitors in axSpA, with approximately 50% of patients achieving a clinically important response,5 we reasoned that molecular imaging studies aiming at selectively visualising TNFα in vivo at the site of clinical inflammation could be an attractive approach. Therefore, we set up a proof-of-concept study in axSpA patients by performing scintigraphy with Tc99m-labelled certolizumab pegol (CZP) as tracer. We investigated the agreement between tracer uptake on immunoscintigrapy and BME on MRI at the same localisation of the SIJ. CZP was conjugated with succinimidyl-6-hydrazino-nicotinamide (S-HYNIC), a bifunctional crosslinker. Subsequently, solutions of 1.25 mg conjugated S-HYNIC CZP were used to radiolabel with Tc99m. Seven axSpA patients (71.4% male; mean age 36±5.7 …
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Handling editor Josef S Smolen
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PC and TR contributed equally.
Correction notice This article has been corrected since it published Online First. The first and second affiliations have been corrected.
Contributors All authors contributed equally to this letter in terms of conception and design of the letter, the acquisition, analysis and interpretation of data. Drafting the work or revising it critically for important intellectual content was performed by DE and FEVdB. DE and FEVdB cosupervised this work.
Funding UCB Pharma SA is the party providing funding and study medication.
Competing interests None declared.
Patient and public involvement Patients and/or the public were not involved in the design, or conduct, or reporting or dissemination plans of this research.
Patient consent for publication Not required.
Ethics approval The study (EudraCT number: 2009-017998-37) was approved by the local ethics committee of the University Hospital of Ghent (Belgium), the Federal Agency for Nuclear Control (Belgium) and Federal Agency for Medicines and Health Products (Belgium).
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement All data relevant to the study are included in the article.