Objective Synovitis in patients with rheumatoid arthritis (RA) may be scored semiquantitatively (0–3) for B-mode (BM) and power Doppler (PD) ultrasonography. The objective was to assess the reliability of BM and PD examinations with a novel ultrasonographic atlas as reference.

Methods Representative ultrasound images (including scores 0–3) of BM and PD from 24 different joints were collected to develop an ultrasonographic atlas. Ten RA patients were assessed twice by five rheumatologists performing BM and PD scoring (0–3) of 16 joints bilaterally (metacarpophalangeal 1–5, wrist (radiocarpal, intercarpal, radioulnar), elbow, knee, talocrural and metatarsophalangeal 1–5), with the novel ultrasonographic atlas as a reference.

Results The median (range) percentages of exact agreements for BM/PD assessments were 73.1 (70.3–80.6)/83.7 (76.7–87.6) and for close agreement 98.1 (96.2–99.7)/98.0 (96.8–98.4) with weighted κ values of median (range) 0.77 (0.70–0.83) for BM and 0.83 (0.73–0.86) for PD. The intrarater intraclass correlation coefficients (ICC) for BM/PD scores were 0.95 (0.93–0.99)/0.97 (0.95–0.99) and interrater ICC were 0.95 (0.86–0.99)/0.97 (0.94–1.00). Scoring of 32 joints was completed in median 15 min (range 12–20).

Conclusion With the use of an ultrasonographic atlas as reference high intra and interrater reliability was found for BM and PD scoring. This novel atlas may be a useful resource in clinical practice and research.