Differentiating Erosive RA With Ultrasound vs Radiography

According to a study published in Joint, Bone, Spine, ultrasound assessments were more sensitive in detecting erosive disease at the joint level in patients with rheumatoid arthritis (RA) compared with radiography, which is the current clinical gold standard for visualizing and quantifying bone lesions.

The investigators of this study sought to compare radiography and ultrasound techniques for characterizing erosive lesions in patients with RA and osteoarthritis (OA), including prevalence, topography, and severity. The investigators further sought to establish diagnostic thresholds for erosive RA based on these approaches and to assess the performance of ultrasound vs radiography in determining a differential diagnosis.

The study sample included a total of 168 patients who fulfilled American College of Rheumatology ACR) 1987 or ACR/European League Against Rheumatism (EULAR) 2010 criteria for RA (n=122) and ACR criteria for OA of the hand (n=46). Based on radiography assessment, patients were evaluated independently for erosive RA by 2 blinded readers who performed a modified Sharp erosion score with sub-scores for hands and feet. Erosive disease was defined as erosion observed in at least 3 separate facet joints at sites of the hands and feet. For the ultrasound assessment, investigators systematically examined 6 bilateral joints using a 4-grade scale to calculate total ultrasound score for erosions: grade 0=no erosion; grade 1=single erosion <2 mm; grade 2=single erosion ≥2 mm or 2 erosions <2 mm; and grade 3=single erosion ≥3 mm or multiple erosions. Diagnostic performances and threshold confirmation for erosive RA were analyzed and compared for both radiography and ultrasound techniques.

For radiography assessments, 42 patients with RA and 5 patients with OA met the definition of erosive disease according to EULAR 2013 criteria. A diagnostic threshold of 3 eroded joints was confirmed with a sensitivity rate of 34.4% and a specificity rate of 89.1%. For ultrasound assessments, 95 patients with RA and 12 patients with OA had eroded facet joints. The diagnostic threshold based on ultrasound was defined as 2 eroded joints or at least one grade 2 erosion with good sensitivity (68% to 72.1%) and excellent specificity (89.1% to 100%). By this definition, 83 patients with RA and no patients with OA satisfied a diagnosis of erosive disease. Comparing performance, the agreement between radiography and ultrasound thresholds was excellent (90.4% to 92.8%). The positive and negative likelihood ratios for radiography (3 eroded joints) were 3.16 and 0.73, respectively, and for ultrasound (2 eroded joints) were 6.64 and 0.31, respectively.

Compared with radiography, the study investigators found that ultrasound had superior sensitivity and similar specificity for detecting erosive disease, noting that ultrasound detected about 2 times more patients with erosive RA compared with radiography.

Reference          

Roux C, Gandjbakhch F, Pierreisnard A, et al. Ultrasonographic criteria for the diagnosis of erosive rheumatoid arthritis using osteoarthritic patients as controls compared to validated radiographic criteria [published online January 31, 2019]. Joint Bone Spine. doi: 10.1016/j.jbspin.2019.01.011