Correlation of US-7 and US-9 Scores with Disease Activity Score using 28 Joint Counts (DAS28) in Patients with Rheumatoid Arthritis

Background: The attentive management of rheumatoid arthritis (RA) has attracted particular attention. The German 7-joint Ultrasound (US-7) is the first scoring system that combines bone erosions and soft tissue lesions in a single composite scoring system. This study aimed to assess the correlation between US-7 and Disease Activity Score Using 28 Joint Counts (DAS28) in clinically active RA patients. The efficacy of a novel ultrasound score-based system, the US-9 score (joints assessed with US-7 plus knees), was also compared with the standard US-7 score.Methods: All the RA patients referred to the outpatient rheumatology clinic of Ghaem Hospital, Mashhad, Iran, during 2019-2020 were included. 28 joints were clinically examined to calculate DAS28. Nine joints were assessed comprising the German US-7 plus knees using grayscale ultrasonography (GSUS) and power Doppler ultrasonography (PDUS). Retrieved data were analyzed by SPSS software, version 22. The Spearman Correlation test was used to find the correlation between DAS28 and ultrasonographic findings. The statistical significance level was set at P 0.05. Results: This study was composed of thirty-five RA patients with a mean age of 49.1±12.0 years. US-7 synovitis scores in GSUS and PDUS were significantly correlated with DAS28 (P=0.02, r=0.38 and P=0.003, r=0.48, respectively). US-9 synovitis scores in GSUS and PDUS were also significantly correlated with DAS28 (P=0.003, r=0.49 and P=0.006, r=0.45, respectively). The synovitis score measured by GSUS was significantly correlated with the GSUS knee synovial score (P=0.01, r=0.42).Conclusion: Ultrasound assessment of large joints such as knees can be an effective approach to determining RA severity. However, it can be proposed that adding more involved joints into the sonographic assessment does not necessarily provide a better clinical correlation.