The use of ultrasound appears to be a reliable means of evaluating subtalar joint (STJ) synovitis in patients with rheumatoid arthritis (RA), according to the results of an Outcome Measures in Rheumatology (OMERACT) reliability exercise published in The Journal of Rheumatology.

The investigators sought to assess the interobserver and intraobserver reliability of the ultrasound evaluation of STJ synovitis in individuals with RA. An ultrasound reliability exercise was performed by 12 sonographers in 10 patients with RA and hindfoot pain. B-mode and power Doppler techniques were utilized to assess anteromedial, posteromedial, and posterolateral STJ based on an agreed-upon ultrasound protocol using a 4-grade semiquantitative grading score for synovitis (synovial hypertrophy and signal), along with a dichotomous score for the presence of joint effusion. 

Mean-weighted Cohen’s kappa for synovial hypertrophy, power Doppler, and joint effusion were 0.80 (95% CI, 0.62-0.98), 0.61 (95% CI, 0.48-0.73), and 0.52 (95% CI, 0.36-0.67), respectively. Moreover, weighted Cohen’s kappa for synovial hypertrophy, power Doppler, and joint effusion in the anteromedial, posteromedial, and posterolateral STJ were –0.04 to 0.79, 0.42 to 0.95, and 0.28 to 0.77; 0.31 to 1.00, –0.05 to 0.65, and –0.20 to 0.69; and 0.66 to 1.00, 0.52 to 1.00, and 0.42 to 0.88, respectively.


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Weighted Light’s kappa was 0.67 (95% CI, 0.58-0.74) for synovial hypertrophy, 0.46 (95% CI, 0.35-0.59) for power Doppler, and 0.16 (95% CI, 0.08-0.27) for joint effusion. Furthermore, Weighted Light’s kappa for synovial hypertrophy, power Doppler, and joint effusion were 0.63 (95% CI, 0.45-0.82), 0.33 (95% CI, 0.19-0.42), and 0.09 (95% CI, –0.01 to 0.19) for the anteromedial STJ; 0.49 (95% CI, 0.27-0.64), 0.35 (95% CI, 0.27-0.40), and 0.04 (95% CI, –0.06 to 0.10) for the posteromedial STJ; and 0.82 (95% CI, 0.75-0.89), 0.66 (95% CI, 0.56-0.80), and 0.18 (95% CI, 0.04-0.34) for the posterolateral STJ, respectively.

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The investigators concluded that using multi-site assessment ultrasound seems to be a reliable tool for examining synovitis of STJ in patients with RA. Larger studies are warranted in order to demonstrate that these findings are valid in clinical settings with less-experienced sonographers as well.

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Reference

Bruyn GAW, Siddle HJ, Hanova P, et al. Ultrasound of subtalar joint synovitis in patients with rheumatoid arthritis: results of an OMERACT reliability exercise using consensual definitions [published online November 1, 2018]. J Rheumatol. doi:10.3899/jrheum.171490