Development of a feasible and responsive ultrasound inflammation score for rheumatoid arthritis through a data-driven approach.

OBJECTIVE: To develop and validate a responsive and feasible ultrasound inflammation score for rheumatoid arthritis (RA).

METHODS: We used data from cohorts of early RA (development) and established RA starting/switching biologic therapy (validation). 4 tendons and 36 joints were examined by a grey scale (GSUS) and power Doppler semiquantitative ultrasound (PDUS) scoring system (full score). Ultrasound score components were selected based on factor analyses of 3-month change in the development cohort. Responsiveness was assessed by standardised response means (SRMs). We assessed the proportion of information retained from the full score by linear regression.

RESULTS: 118 patients with early and 212 patients with established RA were included. The final ultrasound score included 8 joints (metacarpophalangeal 1-2-3, proximal interphalangeal 2-3, radiocarpal, metatarsophalangeal 2-3) and 1 tendon (extensor carpi ulnaris) examined bilaterally. The 6-month SRMs for the final score were -1.24 (95% CI -1.47 to -1.02) for GSUS, and -1.09 (-1.25 to -0.92) for PDUS in early RA, with 87% of total information retained for GSUS and 90% for PDUS. The new score performed somewhat better than formerly proposed scores in the validation cohort.

CONCLUSIONS: The Ultrasound in Rheumatoid Arthritis 9 joint/tendon score (USRA9) inflammation score showed good responsiveness, retained most of the information from the original full score and overall performed better than previous scores in a validation cohort.

TRIAL REGISTRATION NUMBERS: NCT01205854, ACTRN12610000284066; Post-results.