Background/Purpose:

Early diagnosis of RA and effective monitoring of disease activity are important for treatment decision-making. Early treatment strategies can be effective in preventing the development of erosive disease. The primary method of assessing disease activity with physical examination of swollen and tender joints has low accuracy and reliability but remains the cornerstone of assessment despite new imaging modalities. This study examines early RA disease activity in feet with clinical assessment and its correlation with findings on US and MRI, the latter being the reference standard.

Methods:

Treatment naive patients with early RA (ACR criteria, <2 years of symptom duration) were recruited. The most clinically symptomatic foot was assessed for swelling and tenderness in the metatarsophalangeal joints (MTPJ) 2-5. The same foot was imaged by US (Esaote MyLab70, 6-18 MHz linear array probe) and a peripheral MRI (1.0 Tesla, GE Medical). US images were semi-quantitatively graded for synovial thickening (0-3) and Power Doppler (PD) (0-3), representing hypervascularization by the rheumatologist who performed clinical assessments. Based on OMERACT RA MRI scoring criteria, a radiologist blinded to clinical and US results semi-quantitatively graded MTPJ 2-5 for bone marrow edema (BME) (grade 0-3 per metatarsal head and phalanx base, max=24) and synovitis (grade 0-3 per MTPJ, max=12).

Results:

Included in the analyses were 39 patients; 33 female (84.6%), mean (SD) symptom duration 12.2 months (10.9), 18 anti-CCP positive (46.2%), and15 RF positive (38.5%). Mean CRP and ESR levels were 18.9 mg/L (30.7) and 28.4 mm/hr (22.4), respectively. Of the 31 swollen MTP joints, 81% had synovial thickening on US, and of these joints, 44% showed PD and 64% had synovitis or BME grade ≥2 on MRI. Of 125 MTP joints assessed as not swollen, 41% (51 joints) were found to have synovial thickening on US with 22% also showing PD and 38% with synovitis or BME grade ≥2. Of the 39 patients, 18 had ≥1 swollen joint and, of this subset, 94% had synovial thickening, with 41% showing PD and 57% having synovitis or BME grade ≥2. Of the 21 patients without swelling, 86% (18 patients) had synovial thickening in ≥1 joint, with 28% showing PD and 40% having synovitis or BME grade ≥2.

Conclusion:

In examining patients with early RA, joints with synovial thickening and PD on US are also found to have inflammation on MRI. Making treatment decisions based solely on clinical presentation might result in under treatment of a fairly high proportion of patients with sub-clinical inflammation. These findings are suggestive that US with evidence of synovial thickening and PD may be helpful as an adjunct to clinical examination in assessing disease activity.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/sub-clinical-disease-activity-in-the-feet-of-patients-with-early-rheumatoid-arthritis-what-clinical-assessments-miss/