Do NSAIDs Mask MRI Findings in Patients with Axial Spondyloarthritis?

Research suggests that the diagnosis and classification of axial spondyloarthritis (axSpA) via magnetic resonance imaging (MRI) may be hindered when patients are taking non-steroidal anti-inflammatory drugs (NSAIDs). Data from this study were presented by Gareth T. Jones, PhD, of the Epidemiology Group, Aberdeen Centre for Arthritis and Musculoskeletal Health, University of Aberdeen, U.K., during the British Society for Rheumatology Annual Conference, April 24–26.¹

Background

MRI is frequently used to diagnose and classify axSpA with imaging evidence of active sacroiliitis (i.e., sacroiliac joint bone marrow edema). NSAIDs are first-line medications used to relieve and treat persistent symptoms of axSpA. Although NSAIDs are often prescribed by primary care physicians, many NSAIDs are available without a prescription. Thus, when patients first see a rheumatologist, they may already be taking an NSAID.²

Jones et al. hypothesized that such NSAID use may lead to an underestimation of sacroiliac joint bone marrow edema and mask the actual amount of joint inflammation present in patients with axSpA. They investigated the effects of NSAIDs on MRI exams in this patient population.

Methods

Adult patients with axSpA were enrolled from National Health Service rheumatology clinics. Patients were asked to discontinue their use of NSAIDs for one to two weeks before undergoing a sacroiliac joint MRI (scan 1). All study participants were then asked to restart their NSAID treatment.

Patients with bone marrow edema on scan 1 underwent a second scan six weeks after restarting their NSAID treatment. In the study, bone marrow edema lesions were defined according to the Assessment of SpondyloArthritis International Society (ASAS) criteria.

All scans were independently read by two different individuals and adjudicated by a third individual, if needed. All scan readers were blinded to the patients’ clinical characteristics and time point in the study. The researchers sought to determine the proportion of participants who had a no (or reduced) inflammation indicated on a second scan when they were taking NSAIDs vs. inflammation on a first scan when they were not taking NSAIDs.

Results

The researchers recruited 311 patients from 34 medical centers. Patient baseline characteristics included a median age of 42 years (mean interquartile range: 32–52 years). Sixty-two percent of patients were men (n=194), and 87% were white (n=271). The median symptom duration was nine years (mean interquartile range: 4–20 years), and the median time since diagnosis was one year (mean interquartile range: 0­–7 years). The median Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) was 4.5 (mean interquartile range: 2.8–6.2), the median Bath Ankylosing Spondylitis Functional Index (BASFI) was 3.1 (mean interquartile range: 1.5–5.6), and an elevated C-reactive protein of greater than 4 mg/dL was found in 46% of patients (n=143).