Background/Purpose: Rheumatoid arthritis (RA) is a chronic inflammatory disease leading to joint destruction. Serologically, it can be differentiated according to rheumatoid factor (RF), anti-cyclic-citrullinated-peptide antibodies (anti-CCP) or both. This differentiation is prognostically and therapeutically relevant. No method has been described to separate the two forms phenotypically. We hypothesize that a differentiation is possible by evaluating oscillation patterns in power Doppler sonography (PDS).

Methods: In a prospective study, 20 patients with anti-CCP-positive RA and 20 patients with anti-CCP-negative RA with active wrist synovitis were examined. A PDS scan was performed, and perfusion maxima (Pmax) and minima (Pmin) as well as the difference (ΔP) were determined by a blinded study member. The difference was standardized (sΔP) by dividing by Pmax, and the anti-CCP-positive and -negative patients as well as the RF-positive and -negative were compared to each other.

Results: In the ultrasonographic evaluation we found a highly significant difference in sΔP between anti-CCP positive and anti-CCP negative patients (Median 19.01% vs. 42.92%, p<0.0001) (Fig.1). sΔP is independent of disease activity. ΔP did not differ between the groups. Also, in anti-CCP-positive patients there was a completely linear correlation between Pmax and Pmin, this was far less marked in anti-CCP-negative patients (Fig.2). The difference between RF positive and RF negative patients was significant, but less pronounced than for anti-CCP.

Conclusion: Anti-CCP-positive and anti-CCP-negative RA display different PDS oscillation patterns. This constitutes a non-serological parameter to differentiate between the two forms. The difference in PDS oscillation patterns suggests that the underlying pathological process differs between the forms.