18F-FDG positron emission tomography as a marker of disease activity and treatment response in ankylosing spondylitis and psoriatic arthritis

The ability of 18 F-FDG positron emission tomography (PET) to track disease activity and treatment response in patients with Ankylosing Spondylitis (AS) or Psoriatic Arthritis (PsA) remains unclear. Here, we assessed whether 18 F-FDG uptake is a marker of disease activity and treatment response in AS or PsA, and explored the ability of 18 F-FDG to predict treatment response. Patients with AS (n = 16) or PsA (n = 8) who were scheduled to initiate treatment with biologics were recruited. Participants underwent a clinical evaluation and an 18 F-FDG scan prior to therapy initiation. Eleven participants underwent a follow-up 18 F-FDG scan 3 months post-treatment. Images were quantified using a composite measure that describes the inflammatory status of the patient. Clinically involved joints/entheses had higher 18 F-FDG uptake compared to unaffected areas (median difference > 0.6, p 8.5, p