Effect of Nonsteroidal Anti-Inflammatory Drugs on Sacroiliac Joint Inflammation, as Seen on Magnetic Resonance Imaging, in Axial Spondyloarthritis

Objective: Imaging evidence of active sacroiliitis is important for diagnosis, classification, and monitoring of axial spondyloarthritis (axSpA). However, there is no consistent guidance on whether patients should temporarily stop nonsteroidal anti-inflammatory drugs (NSAIDs) before magnetic resonance imaging (MRI). The aim of this study was to determine whether NSAIDs lead to an underestimation of active sacroiliitis, as observed using MRI. Methods: Adults with axSpA were recruited from rheumatology clinics and undertook NSAID washout for one to two weeks before a sacroiliac joint MRI scan. Images were read by two independent readers and adjudicated by a third if required. Those who had a positive result for active sacroiliitis, as per internationally recognized criteria, underwent a second scan six weeks after recommencing daily NSAIDs. We determined the proportion of participants who had a negative scanning result while taking NSAIDs after a previous positive result when NSAID-free. Images were also scored using semiquantitative methods comprising lesion size and intensity, and a subset of participants underwent quantitative MRI (qMRI) to provide an objective evaluation of any inflammatory changes. Results: From 34 centers across the United Kingdom, 311 participants (median age 42 years; 62% male) were recruited; 286 (92%) completed the NSAID washout and underwent the first MRI scan. From 146 participants with active sacroiliitis, follow-up scans (while taking NSAIDs) were obtained from 124 (85%), at which point 25 participants had a negative result (20.2%; 95% confidence interval 13.5%–28.3%). Semiquantitative and qMRI methods supported these findings. Conclusion: One-fifth of patients showed full resolution of active sacroiliitis lesions when NSAIDs were present. In clinical practice, if patients with axSpA are willing to attempt a one- to two-week NSAID washout before MRI, this should be considered.