When Arthralgia Signals Imminent Rheumatoid Arthritis

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Key points
• The recent European League Against Rheumatism (EULAR) definition of arthralgia suspicious for progression to rheumatoid arthritis (RA) is sensitive when combined with a rheumatologist's opinion.

• The EULAR definition serves to solidify the rheumatologist's diagnosis of at-risk patients.

• To achieve a high level of specificity, the EULAR definition of arthralgia suspicious for progression to RA should be combined with biomarker studies.

Background
To develop better treatment strategies for RA, the focus of research has shifted to very early disease phases. A EULAR taskforce developed a definition for arthralgia suspicious for progression to RA in an effort to include patients likely to develop RA in research studies.

Burgers and colleagues¹ in the Netherlands point out that a rheumatologist's suspicion that an arthralgia will progress to RA has a sensitivity and a specificity of 80% and 93%, respectively. The development of a specific definition was undertaken in an effort to remove some of the subjectivity inherent in an individual rheumatologist's opinion.

The researchers sought to validate the definition of arthralgia suspicious for progression to RA in an effort to solidify its use in identifying such patients. They recently presented their findings in Rheumatology.

The study
The authors conducted a longitudinal validation study that included 241 patients in the clinically suspected arthralgia (CSA) group from Leiden. The subjects had a recent diagnosis of small joint arthralgia at risk for progression to RA. A second cohort of 113 patients was referred by general practitioners in Umea, Sweden, for arthralgia of the small joints.

The results
• 74% of patients in the CSA group met the definition criteria for arthralgia suspicious for progression to RA.

• 18% of subjects in the CSA group went on to develop arthritis between 6 and 22 weeks later.

• Subjects who met the definition had a greater likelihood of developing arthritis (hazard ratio, 2.1; 95% confidence interval, 0.9-4.7).

• In the cohort referred by general practitioners in Umea, 27% of subjects met the definition criteria; however, definition-positive subjects did not develop arthritis more often than definition-negative patients (3% versus 11%).

Implications for clinicians
• The EULAR definition of arthralgia suspicious for progression to RA is valid.

• Validity of the definition is sensitive and valuable only when used to support an expert's clinical opinion.

• The definition "should only be applied in secondary care in patients in whom, according to the rheumatologist, imminent RA is the most likely diagnosis."¹

• These results increase homogeneity in patients thought to be at risk for RA.

• For maximum sensitivity, the EULAR definition should be combined with biomarker evidence for imminent RA.

References:

1. Burgers LE, Siljehult F, Ten Brinck RM, et al. Validation of the EULAR definition of arthralgia suspicious for progression to rheumatoid arthritis. Rheumatology. 2017;56:2123-2128. doi:10.1093/rheumatology/kex324.