US is a promising tool in evaluating RA synovitis, but abnormal US findings have been reported in small subsets of normal joints in healthy subjects. This study aimed to systematically assess greyscale US (GSUS) and power Doppler US (PDUS) findings in 40 peripheral joints-the 28-joint DAS (DAS28) set, ankles and MTP joints-in healthy subjects. A composite score of abnormal US findings in 40 joints was compared with serum levels of pro-inflammatory cytokines.
US of 60 standard views in 40 joints was performed in 30 healthy subjects (total 3600 images). GSUS and PDUS were scored semi-quantitatively (0-3). Serum samples were obtained at the time of US and analysed for IL-1α, IL-1β, IL-2, IL-6, IL-8, VEGF, TNF-α and IFN-γ using biochip array technology.
GSUS abnormalities were more frequent than PDUS abnormalities [mean total GSUS score = 20.07 (range 6-45; maximum potential score = 180), mean total PDUS score = 4.8 (range 0-13)]. GSUS score increased with increasing age (Spearman's ρ = 0.383, P = 0.037). A PDUS signal >1 was observed only in the wrist (8%) and MTP1 (3%). GSUS scores did not correlate with any pro-inflammatory cytokine level. The total PDUS score correlated significantly with serum VEGF (r = 0.395, P = 0.046).
PDUS signals >1 are rarely seen in normal synovial joints. GSUS synovitis, but not PDUS, may reflect age-related joint changes. PDUS correlated with VEGF, providing further evidence of a central role for VEGF in synovial neo-angiogenesis.