Background/Purpose:

Ultrasound (US) is widely used by rheumatologists to assess inflammatory burden on patients with inflammatory arthritis. Some studies have shown that US measures of inflammation reflects aspects of histological synovitis in a heterogeneous groups of patients with rheumatoid arthritis (RA). Little work has been done to describe this relationship in an early arthritis population.

Our aim of this study is to investigate, at a single joint level, the correlation of US synovitis with histological synovial inflammation before and after treatment initiation in a homogenous cohort of patients with early RA.

Methods:

Data was collected from 54 patients with early RA (fulfills 1987 ACR classification, symptom onset <12 months). Patients were naïve to both disease modifying anti-rheumatic drugs (DMARD) and to steroids. All patients underwent a core data set assessment including clinical, biochemical, imaging and an US guided minimally invasive synovial biopsy of the most inflamed joint. Patients were then initiated on DMARD according to standardised protocol. A repeat assessment and US guided biopsy was performed at 6 months follow up. US images of the joint are scored using a semi quantitative score (0-3). Sections of paraffin embedded synovial tissue received immunohistochemical staining for CD3, CD20, CD68, CD68sland CD138 and these parameters were graded in a semiquantitative fashion (0-4). Spearman's rho was used to correlate scores at each time point.

Results:

At baseline, US power doppler (PD) was significantly correlated with histological markers of inflammation – CD3 (r=0.43, p<0.05), CD20 (r=0.46, p<0.01), CD68 (r=0.37, p<0.05), CD68sl (r=0.46, p<0.01) and CD138 (r=0.61, p<0.001), and with inflammatory markers erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) (r=0.4, p <0.05).  After 6 months of therapy, most of these correlations were still present, most notably with CD68sl (p<0.05). Interestingly, we also found that a fall in US PD in response to treatment at 6 months is associated with a fall in CD68sl (r=0.50, p<0.005) and a fall in DAS28 (r= 0.40, p<0.05).

Conclusion:

US PD has long been recognised as an accurate reflection of disease activity in inflammatory arthritis. Our results have shown that US PD also reflects synovial inflammation at a histopathological level. The association of US PD, CD68sl and DAS28 supports the current opinion that Power Doppler US is a biomarker for treatment response and reflects both clinical and histological markers of disease activity in patients with RA.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/ultrasound-synovitis-reflects-synovial-inflammation-at-a-histopathological-level/