MRI-Detected Erosions May Not Be Specific to Rheumatoid Arthritis

MRI of the foot.
MRI of the foot.
Erosions may also be detected in patients with other arthritides and in symptom-free individuals.

Erosions detected by MRI should not be overestimated in the diagnosis of rheumatoid arthritis (RA), as they may be detected in patients with other arthritides and in symptom-free persons from the general population, according to a study published in the Annals of Rheumatic Diseases.

Although MRI is recommended for detecting early joint damage in RA, MRI-detected erosions may also present in symptom-free control patients, especially at older age. Whether RA-specific MRI-detected erosions can be distinguished from physiological erosions in symptom-free persons is currently unknown.

Researchers evaluated MRIs of unilateral metacarpophalangeal (MCP) and metatarsophalangeal (MTP) joints in 589 patients with early arthritis (238 patients with RA, 351 patients with other arthritides) and 193 symptom-free control patients. The participants were further categorized by age group (<40 years, 40-59 years, ≥60 years), and total erosion scores, number, severity, location of erosions, and simultaneous presence of MRI-detected inflammation (synovitis or bone marrow edema) were compared.

The investigators found that MRI-detected erosions in MCP and MTP joints were not confined to RA, but were also present in patients with other arthritides and in symptom-free persons from the general population. Although patients with RA had statistically significant higher total erosion scores than control patients, scores of individual patients largely overlapped. Some erosion characteristics were identified as specific for RA (grade ≥2 erosions, fifth metatarsophalangeal joint erosions, and first metatarsophalangeal joint erosions if aged <40 years), although these occurred in only 21% of patients.

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“The present data imply that if single measurements with novel imaging modalities such as MRI are used for the early detection of structural damage in clinical practice, the risk of false-positive findings should be considered,” the authors concluded. Longitudinal MRI may improve specificity, the authors suggested, although this was not specifically tested in this study.

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Boeters DM, Nieuwenhuis WP, van Steenbergen HW, et al. Are MRI-detected erosions specific for RA? A large explorative cross-sectional study [published online February 28, 2018]. Ann Rheum Dis. doi:10.1136/annrheumdis-2017-212252