Factors influencing concordance between clinical and ultrasound findings in rheumatoid arthritis.

Objective: Clinical joint examination (CJE) is less time-consuming than ultrasound (US) in rheumatoid arthritis (RA). Low concordance between CJE and US would indicate that the 2 tests provide different types of information. Knowledge of factors associated with CJE/US concordance would help to select patients and joints for US. Our objective was to identify factors associated with CJE/US concordance.
Methods: Seventy-six patients with RA requiring tumor necrosis factor-α (TNF-α) antagonist therapy were included in a prospective, multicenter cohort. In each patient, 38 joints were evaluated. Synovitis was scored using CJE, B-mode US (B-US), and power Doppler US (PDUS). Joints whose kappa coefficient (κ) for agreement CJE/US was < 0.1 were considered discordant. Multivariate analysis was performed to identify factors independently associated with CJE/US concordance, defined as factors yielding p < 0.05 and OR > 2.
Results: Concordance before TNF-α antagonist therapy varied across joints for CJE/US (κ = -0.08 to 0.51) and B-US/PDUS (κ = 0.30 to 0.67). CJE/US concordance was low at the metatarsophalangeal joints and shoulders (κ < 0.1). Before TNF-α antagonist therapy, a low 28-joint Disease Activity Score (DAS28) was associated with good CJE/B-US concordance, and no factors were associated with CJE/PDUS concordance. After TNF-α antagonist therapy, only the joint site was associated with CJE/B-US concordance; joint site and short disease duration were associated with CJE/PDUS concordance.
Conclusion: Concordance between CJE and US is poor overall. US adds information to CJE, most notably at the metatarsophalangeal joints and shoulders. Usefulness is decreased for B-US when DAS28 is low and for PDUS when disease duration is short.