SAN DIEGO – Healthy individuals can show signs of spinal and pelvic inflammation on MRI, but these scans can be misleading if relied on to make a diagnosis of axial spondyloarthritis, according to findings from three separate studies at the annual meeting of the American College of Rheumatology.
“Don’t rely on MRI alone is our message,” said Robert Landewé, MD, PhD, of the University of Amsterdam, who was a coauthor of one of the three studies. “A positive MRI may occur in individuals that are completely healthy. We need to make sure that not too many patients with chronic lower back pain are diagnosed with a disease they don’t have.”
The axial form of spondyloarthritis (axSpA) affects the spinal and pelvic joints of an estimated 1.4% of the U.S. population, and the term encompasses the diagnosis of ankylosing spondylitis (0.5% of U.S. population) in which advanced sacroiliitis is seen on conventional radiography, according to the ACR. Axial SpA is particularly common in young people, especially males, in their teens and 20s.
Researchers believe that MRI scans can misleadingly suggest that patients have the condition. “We know that MRI is a sensitive method, but there’s a lack of data regarding its specificity,” Thomas Renson, MD, of Ghent (Belgium) University, said at a press conference during the meeting.
Dr. Landewé led a study that compared MRIs of sacroiliac joints in 47 healthy people, 47 axSpA patients matched for gender and age, 47 chronic back pain patients, 7 women with postpartum back pain, and 24 frequent runners. Positive MRIs were common in the axSpA patients (43 of 47), but they were also found in healthy people (11 of 47), chronic back pain patients (3 of 47), frequent runners (3 of 24), and women with postpartum back pain (4 of 7).
In another study, Dr. Renson and his colleagues sought to understand whether a sustained period of intense physical activity affected spinal findings in 22 healthy military recruits who did not have SpA.
Dr. Ulrich Weber
The recruits underwent scans before and after 6 weeks of intensive training. “All the recruits followed the same daily training program, lived in the same housing, and were in same environmental conditions,” Dr. Renson said. Bone marrow edema (BME) and structural lesions were common in the recruits both before and after training, but the differences weren’t statistically significant. The same was true for positive MRIs. This may be because the bones of the recruits had already been under physical strain due to their existing abilities, Dr. Renson said, and didn’t respond to additional activity.
However, there was a statistically significant increase of combined structural and inflammatory lesions (P = .038) from baseline to post training.
The findings underscore “the importance of interpretation of imaging in the right clinical context,” Dr. Renson said, since they point to the possibility of an incorrect diagnosis “even in a young, active population.”
Another study, led by Ulrich Weber, MD, of King Christian 10th Hospital for Rheumatic Diseases, Gråsten, Denmark, sought to understand levels of normal low-grade BME in 20 amateur runners (8 men) and 22 professional Danish hockey players (all men). On average, the researchers found signs of BME in 3.1 sacroiliac joint quadrants in the runners before and after they ran a race. Hockey players were scanned at the end of the competitive season and showed signs of BME in an average of 3.6 sacroiliac joint quadrants.
In an interview, Dr. Landewé said the studies point to how common positive MRIs are in healthy people. “It was far higher than we would have thought 10 years ago,” he said.
Are MRIs still useful then? Dr. Weber said MRI scans are still helpful in axSpA diagnoses even though they have major limitations. “The imaging method is the only one that’s halfway reliable,” he said. “These joints are deep in the body, so we have virtually no clinical ways to diagnose this.”
However, Dr. Landewé said, “you should do it only when you have sufficient suspicion of spondyloarthritis” – due to accompanying conditions such as positive family history, acute anterior uveitis, psoriasis, or peripheral arthritis – and not just when a patient has chronic back pain.
Dr. Renson reported having no relevant disclosures; two of his coauthors reported extensive disclosures. Dr. Weber and his coauthors reported having no relevant disclosures. Dr. Landewé reported having no relevant disclosures; several of his coauthors reported various disclosures. Funding for the studies was not reported.