A series of studies indicate that physicians should be wary of relying solely on MR when diagnosing axial spondyloarthritis (axSpA) in patients.

The findings presented last week at the at the 2017 ACR/ARHP Annual Meeting in San Diego suggest that MR scans of the sacroiliac joints are prone at times to produce positive results for axSpA in healthy individuals who do not have the condition, ushering in the need for additional diagnostics to confirm the presence of the condition.

“Only recently have we realized that there is a lot of diagnostic ‘overcall’ regarding MR of the sacroiliac joints,” Robert B.M. Landewé, a professor of rheumatology at the University of Amsterdam in the Netherlands and the lead author of one of the studies, told HCB News. “In addition, physicians tend to value a positive MR test result as proof for the presence of spondyloarthritis. Such a strong belief is only justified if healthy individuals do not have positive MRs but increasing evidence suggests that healthy people may score positive.”

Healthy patients who receive a positive MR finding for axSpA may incur harm from exposure to expensive and potentially toxic biologicals used to treat the condition.

The study involving Landewé consisted of three trained, blinded readers scoring MR scans of 47 healthy individuals, 47 gender- and age-matched participants with confirmed cases of axSpA, 47 age- and gender-matched back pain patients irrespective of MR results, seven women with postpartum back pain lasting several months and 24 frequent runners.

AxSpA patients were selected from the SPondyloArthritis Caught Early (SPACE) cohort. MR scans were scored on the basis of the Assessment of Spondyloarthritis (ASAS)/Outcome Measures in Rheumatology (OMERACT) and the Spondyloarthritis Research Consortium of Canada (SPARCC) definitions, with SPARCC scores being the mean result of the three readers.

The presence or absence of bone marrow edema (BME) was agreed upon by the three in 75.6-79.9 percent of cases. Eleven healthy individuals were found to have positive MRs compared to forty-three of the axSpA patients and three chronic back pain participants. Three runners and four women with postpartum back pain had positive MR results for sacroiliac, an inflammation of one or both sacroiliac joints that can be associated with axSpA.

SPARCC scores among the three also correlated well with mean results of 1.7 for healthy participants, 20.9 for positive axSpA patients, 0.8 for chronic back pain patients, 0.8 for frequent runners and 4.5 for women with postpartum back pain.

Under a system with a score of two as the cut-off for positivity, 12 healthy individuals were diagnosed with axSpA along with 46 actual axSpA patients, five chronic back pain patients, four runners and four women with postpartum back pain. When the cut-off was raised to five or greater, four healthy individuals were found to be positive compared to 41 axSpA participants, one chronic back pain patient and two women with postpartum back pain. No runners were declared positive under these scores.

Researchers, in studying the occurrence of deep BME lesions, concluded such lesions to be a separate matter from sacroiliitis in axSpA patients, finding none in healthy individuals, chronic back pain patients or frequent runners. Lesions were found in 38 axSpA patients and in one woman with postpartum back pain.

Landewé says the results of this study and the others reflect the need for caution in evaluating MR scans for the potential presence of axSpA, and should serve as a reminder to physicians to look at all diagnostic exams performed before determining a diagnosis.

“Use MR, but interpret the results cautiously and in the context of the entire clinical picture (‘pattern recognition’),” he suggests. “Do not rely on a positive MR in a patient without a fitting clinical picture.”

The study was presented alongside a series of others, two of which evaluated positive MR scans for axSpA through the examination of joint damage in military recruits, and the occurrence of BME in young athletes.