Research highlighted at the 2017 annual meeting of the American College of Rheumatology (ACR) and the Association of Rheumatology Health Professionals (ARHP) encourages rheumatologists to exercise caution when interpreting magnetic resonance imaging (MRI) scans for the diagnosis of axial spondyloarthritis (SpA), an inflammatory disease with the main symptom of pain in the lower back.
The researchers examined a non-SpA population to elucidate the specificity of MRI in detecting bone marrow edema (BME) and structural lesions that may lead to diagnosis of axial SpA. According to Thomas Renson, MD, a researcher at Ghent University in Belgium and a lead author of the study, MRI scans of healthy military recruits showed sacroiliac joint damage similar to that found in axial SpA after just six weeks of intensive physical training.
“MRI is a sensitive method for the detection of active sacroiliitis, but there is limited data regarding its specificity. It is important to evaluate this, considering the risk of over-diagnosing SpA,” Dr. Renson said.
Researchers performed MRI scans on the sacroiliac joints of 22 military recruits before and after six weeks of intense, uniform physical training. Three blinded, trained readers scored BME and structural lesions on the scans. At baseline, 40.9 percent of the recruits presented with at least one BME lesion; at week 6, the number increased to 50 percent. In the recruits who had BME, the mean number of lesions at baseline was 2.4, which rose to 3.7 at week 6. In addition, at baseline, 22.7 percent of recruits had a positive MRI according to the Assessment of Spondyloarthritis (ASAS), which increased to 36.4 percent at follow-up. Structural lesions were observed at baseline in 36.4 percent of recruits, rising to 50 percent after six weeks of training.
The researchers stressed the high prevalence of lesions at baseline and the high proportion of participants who met the ASAS definition of an MRI positive for sacroiliitis.
“Since non-SpA patients can have SpA-like MRI lesions, setting the appropriate clinical indication for imaging is very important,” Dr. Renson said. “MRI can strengthen or weaken your suspicion of SpA, but does not give you 100 percent certainty.”