Power-Doppler perfusion phenotype in RA patients is dependent on anti-citrullinated peptide antibody status, not on rheumatoid factor.

It is not known whether there are any consistent non-serological differences between seropositive and seronegative rheumatoid arthritis, and if any, whether they depend upon rheumatoid factor (RF), anti-citrullinated peptide antibodies (ACPA), or both. In a pilot study, we showed that the two forms could be differentiated using power-Doppler sonography (PDS), and that the difference is ACPA dependent. This extended study explored whether the previous findings could be confirmed. 103 patients 51 ACPA positive (ACPA +), 52 ACPA negative (ACPA -) with active wrist arthritis were examined using PDS. By means of a temporal image series, pulsatility was evaluated over a 3-5-s period, maximum and minimum perfusion signal were determined using a computer program counting the number of coloured pixels for each frame. Maxima (Pmax) and minima (Pmin) were determined, and the standardized peak-to-peak amplitude sA was calculated (sA = (Pmax - Pmin)/Pmax). This parameter was then compared for ACPA + and ACPA- patients. In addition, a multivariate regression was performed, to determine which factors influence sA. sA differed significantly between ACPA + and ACPA- patients [20% (13-26) vs. 41% (32-57), p < 0. 0001]. In the multivariate analysis, age (t = 2.5, p = 0.02) and ACPA status (t = - 4.8, p < 0.0001) were independent predictors of sA. PDS perfusion patterns are different in seropositive and seronegative RA. The difference appears to be ACPA, not RF dependent. This suggests that the underlying pathophysiological process is different in ACPA-positive and ACPA-negative RA.