Background Musculoskeletal ultrasonography (US) has been shown to be helpful for diagnosis and monitoring of rheumatoid arthritis (RA). Although several joint combinations have been demonstrated to be useful in the assessment of RA,12 there is still no consensus in defining the joints to evaluate. As comprehensive evaluation by US in RA is time consuming and not feasible in daily practice, it is important to determine the optimal combinations of minimal number of joints.
Objectives Here we investigated the optimal number and combination of joints to be assessed by power Doppler (PD) US in RA.
Methods PDUS were performed in 24 joints, including all PIP, MCP, bilateral wrist and knee joints, as comprehensive evaluation in 231 patients with RA. PD images were scored semiquantitatively from 0 to 3 in each joint, and total PD score-24 was calculated as the sum of scores of 24 joints. The patients were divided into PD-positive (total PD score-24 ≥ 1) and PD-negative (total PD score-24 = 0) groups. The sensitivity and negative predictive value (NPV) of sum scores of different joint combinations were evaluated. The correlations between total PD score-24 and each joint score or the different sum scores were also assessed.
Results The averages of PD scores were high in bilateral wrist, knee, MCP 2 and 3 joints, while these were low in other MCP and all PIP joints. Higher correlation coefficients were found between total PD score-24 and PD scores of bilateral MCP 2, 3 and wrist joints, whereas correlations between total PD score-24 and PD scores of bilateral knee and all PIP joints were weak. Among the sum PD scores of different joint combinations, sum score of reduced 8 joints (total PD score-8), including bilateral MCP 2, 3, wrist, and knee joints, showed the highest sensitivity and NPV (table 1; 98% and 96%, respectively). Moreover, total PD score-8 showed very high correlation with the total PD score-24 (rs = 0.97, P < 0.01).
Conclusions This study shows that the total PD score-8 has almost the same level of sensitivity as the comprehensive evaluation and correlates well with the comprehensive evaluation. Thus total PD score-8 is simple and useful enough for screening and activity measurement for RA.
Perricone C, Ceccarelli F, Modesti M, et al. The 6-joint ultrasonographic assessment: a valid, sensitive-to-change and feasible method for evaluating joint inflammation in RA. Rheumatology (Oxford) 2012;51:866-73.
Ohrndorf S, Fischer IU, Kellner H, et al. Reliability of the novel 7-joint ultrasound score: results from an inter- and intraobserver study performed by rheumatologists. Arthritis Care Res (Hoboken) 2012;64:1238-43.
Disclosure of Interest None Declared