Patients with chronic back pain suspected of having axial spondyloarthritis (axSpA) should not undergo follow-up MRI of the sacroiliac joint (MRI-SI) within a year if they had a negative baseline MRI-SI, according to investigators.

It is very unlikely that a follow-up MRI-SI will yield new results, reported Pauline A. Bakker, MD, of the department of rheumatology at Leiden University Medical Centre, the Netherlands, and her colleagues.

Since gender and HLA-B27 status were closely associated with MRI-SI positivity, these factors should be considered when deciding to repeat an MRI-SI.

“Over the last decade, MRI rapidly gained ground and proved to be an important imaging technique in the diagnostic process of [nonradiographic] axial spondyloarthritis,” the investigators wrote in Arthritis and Rheumatology. “It has been shown that MRI can detect the early inflammatory stages of sacroiliitis months to years before structural damage can be detected on a conventional radiograph.”

Although MRI represents a diagnostic leap forward, questions of clinical application remain. “For example… if an MRI is completely normal and there is still a clinical suspicion of axSpA, should the MRI be repeated? And if so, after what period of follow-up? Or does this not contribute to the diagnostic process?”

To answer these questions, the investigators observed the “evolution of MRI lesions over a 3-month and 1-year time frame” in patients with early chronic back pain and suspected axSpA.

The prospective study involved 188 patients from the Spondyloarthritis Caught Early (SPACE) cohort. The authors commented that this is “an ideal cohort… since it includes a population of patients with back pain of short duration referred to rheumatologists with a suspicion of SpA [but without the mandatory presence of a single or multiple SpA features].”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.