Repeat MRI not useful in suspected axial spondyloarthritis

Enrolled patients had chronic back pain lasting between 3 months and 2 years, with onset beginning between 16 and 45 years of age. Each underwent physical examination (including evaluation of other SpA features), MRI and radiographs of the sacroiliac joints, and HLA-B27 testing. If patients fulfilled axSpA criteria or had possible axSpA (at least one SpA feature), then they proceeded into the follow-up phase of the study, which included repeat MRI-SI at 3 months and 1 year.

Among enrolled patients, slightly more than one-third were male, almost half were HLA-B27 positive, and about three-quarters had Assessment of Spondyloarthritis International Society–defined inflammatory back pain. Mean age was 31 years; 31 (16.5%) patients were MRI-SI positive.

Of patients that were MRI-SI positive at baseline, 11.1% and 37.9% had a negative MRI-SI at 3 months and 1 year, respectively. The authors noted that this change “was partly induced by the start of anti-TNF [tumor necrosis factor] therapy.” In patients who were MRI-SI negative at baseline, 4.3% and 7.2% were positive at 3 months and 1 year, respectively.

“A very small percentage of patients become positive… which indicates that the usefulness of repeating an MRI-SI in the diagnostic process after 3 months or 1 year is very limited,” the authors wrote.

Gender and HLA-B27 status were independently associated with a positive MRI-SI at any point in time. About 43% of HLA-B27-positive men had a positive MRI-SI, compared with just 7% of HLA-B27-negative women. The investigators advised that these associations be considered when deciding upon repeat MRI-SI.

“If a clinical suspicion [of axSpA] remains [for example, a patient develops other SpA features] it might be worthwhile to consider redoing an MRI in HLA-B27 positive patients,” the investigators wrote. “Likewise, there is a statistically significant difference between male and female patients with a negative baseline MRI, namely that in male patients more often a positive MRI at follow-up is seen [difference: 12% in men, 3% in women].”

The researchers reported having no conflicts of interest.

SOURCE: Bakker PA et al. Arthritis Rheumatol. 2018 Sep 11. doi: 10.1002/art.40718.