Ultrasound (US) provides measurements of synovial morphology and vascularity. However, on an individual joint basis in RA, US measures do not relate well to clinical signs. This study investigates the relationship between composite US measures and the 28-joint disease activity score (DAS28), its components and acute phase markers in adult RA.
RA synovial disease activity was recorded in 50 patients by: (i) the DAS28 score; (ii) ESR and CRP; and (iii) US using Grey scale (GS) and power Doppler (PD) measures of PIP and MCP joints to derive composite US scores based on abnormal counts and severity. A total of 25 control subjects were studied to define normal US appearances. The relation between each measure of synovial disease was determined by Spearman correlation analysis.
There was a significant relation between the DAS28 and the GS joint count (GSJC, Spearman's r = 0.4; P = 0.004) and severity score (GSJS, r = 0.34; P = 0.016) and the PD joint count (PDJC, r = 0.32; P = 0.028). There was a significant relation between the ESR and PDJC (r = 0.37; P = 0.007) and PD joint severity score (PDJS, r = 0.38; P = 0.006) and between the CRP and PDJS (r = 0.29; P = 0.04). The remaining components of the DAS28 related poorly to all US measures, except the tender joint count, which related significantly to the GS but not the PD measures.
Composite US markers of synovial disease relate significantly to the DAS28 score and ESR/CRP in adult RA, but not as well with individual clinical joint counts and the patient's global assessment.