MRI Can Flag Healthy People as Showing Signs of a Chronic Inflammatory Bone Disease
Scans of the sacroiliac joints are often used as a diagnosis tool for axial spondyloarthritis, but new research shows positive results can frequently occur in healthy people, too.
Axial spondyloarthritis (axSpA) is a chronic inflammatory rheumatic disease that predominantly affects the spine and pelvic joints, causing lower back pain. MRI scans of the sacroiliac joints, located between the bottom of the spine and the pelvis, can help physicians diagnose axSpA by highlighting inflammation and damage.
But according to new research, sacroiliac MRI can also appear positive for inflammation in individuals without axSpA and should not be used as the sole method of diagnosis. A team from the Netherlands conducted a study that compared the sacroiliac MRI scans of axSpA patients, healthy subjects, and others to test the specificity of the method. They presented the results last week at the 2017 ACR/ARHP Annual Meeting in San Diego.
In a blind comparison, three trained readers scored MRI scans of the sacroiliac joints from 172 people: 47 healthy individuals; 47 axSpA patients with confirmed, positive MRI whose ages and genders matched the healthy individuals; 47 age- and gender-matched chronic back pain patients; seven women with postpartum back pain lasting several months; and 24 frequent runners. The readers used two different but commonly used scoring systems -- the Assessment of Spondyloarthritis (ASAS)/Outcome Measures in Rheumatology (OMERACT) and the Spondyloarthritis Research Consortium of Canada (SPARCC). The Assessment of Spondyloarthritis International Society developed the ASAS/OMERACT system, which was the first criteria to include findings on sacroiliac MRI. It scores based on the presence of inflammatory lesions. The SPARCC score, a more recently developed system, is based on abnormal increased signal on the MRI scan that represents bone marrow swelling.
While 43 of the 47 axSpA patients had an MRI that scored positive for inflammation in the new study, so did 11 healthy volunteers, 3 chronic back pain patients, 3 runners, and 4 women with postpartum back pain, according to the ASAS/OMERACT definition.
The SPARCC index for scoring inflammation in the sacroiliac joints fared better, with high scores rarely occurring in non-axSpA individuals. The researchers emphasize that a positive MRI alone isn’t enough to diagnosis axSpA, and results from other exams such as an X-ray or blood test should be taken into consideration.