To evaluate the reproducibility of clinical synovitis assessments in rheumatoid arthritis and the effect of variability on the Disease Activity Score-28 (DAS28).
Seven healthcare professionals from different cities examined the same patients with active non-early rheumatoid arthritis (RA; duration > 4 yrs), for whom a treatment change was being considered. There was no training session and the examination was to be performed as quickly as possible. The healthcare professionals assessed the 28 joints of the DAS28 in 7 patients (196 joints), then reexamined the same 28 joints in 4 of these 7 patients (112 joints), who had been rendered unrecognizable. Then 7 sonographers examined each of the 7 patients twice, using B-mode and power Doppler ultrasound (PD). The reference standards were presence of synovitis according to at least 50% of clinical examiners and 50% of sonographers. Agreement was assessed by Cohen's kappa statistic.
Intraobserver reliability ranged from 0.31 (least experienced research technician) to 0.77 (most experienced physician). Interobserver reliability ranged from 0.18 to 0.62. The largest difference between the lowest and the highest swollen joint counts in the same patient was 15, and the greatest variation in the DAS28 score was 0.92. Agreement between clinical and sonographic reference standards was 0.46, 0.37, and 0.36 for B-mode, PD, and both, respectively.
Clinical inter- and intraobserver reliability is highly dependent on the examiner. Consequences on the DAS28 score can be substantial. Agreement with sonography is poor when both B-mode and PD are used but seems better, although low, when B-mode is used alone.