Background Musculoskeletal ultrasonography imposes itself as reliable tool for the disease activity assessment of rheumatoid arthritis (RA) being more sensitive than clinical in detection of synovitis. There is no consensus on the exact joint number should be examined. Naredo et al. developed reduced 12-joint count¹ while Backhaus et al. scored only seven small joints². Although both were found to reflect disease activity it is suitable in a busy clinic to assess the lowest joint count.

Objectives To investigate the validity of 7-joint ultrasonography (US7) scores in assessment of disease activity in Egyptian RA patients compared with simplified 12-joint ultrasonography (US12) scores and correlate both to composite disease activity indices.

Methods Fifty Egyptian RA adult patients diagnosed according to the ACR1987 criteria were subjected to detailed history, 28 tender & swollen joint counts (TJC, SJC). The disease activity was assessed by calculating DAS28-CRP, SDAI and CDAI. The Ultrasonographic assessment was performed using a LOGIQP6 with 10–13 MHz broadband linear array transducer by one well-trained blinded rheumatologist. The synovial hypertrophy on GS & PD images were graded using a semi-quantitative 0–3 scale. The simplified US12 was performed as originally described¹. However the GS & PD synovitis were computed in two separate scores instead of one. The US7 was performed at the clinically dominant side as described by Backhaus et al². Two Sum-US7 scores were added; Sum (GS)-US7 after grading the GS-tenosynovitis and Sum (PD)-US7. Ultrasonography inter/intraobserver reliability was evaluated on 40 stored images using randomization and blinded techniques.The study was approved by the local ethics committee.

Results The studied population had mean disease duration of 89±60 months. 62% were using more than one DMARD. They showed moderate disease activity as defined by DAS28, SDAI and CDAI (mean 3.7±1.4, 19.9±14.9 & 17.9±13.3 respectively). The GS-scores showed no correlation with disease activity parameters. PD-US12, PD (synovitis)-US7 and Sum (PD)-US7 significantly correlated with the SJC, CRP levels (P values 0.03, 0.04 and 0.01) and DAS28 (P values 0.02, 0.009 and 0.001), furthermore Sum (PD)-US7 correlated with SDAI and CDAI (P values 0.013& 0.042 respectively). Correlation coefficient between the different ultrasonographic scores showed no differance. The ultrasonography reliability showed significant agreement (P<0.001). Kappa values were 0.80 & 0.96 for GS & PD interobserver reliability and 0.96 & 1.0 for GS & PD intraobserver reliability.

Conclusions Our results confirm the validity of PD-scores in assessment of disease activity. However they make the significance of GS questionable. The Sum-(PD) US7 seems to perform better than the original one, it was strongly correlated with CRP and with the three disease composite indices. The studied scores correlated with each other favoring the use of less time consuming US7score.

References

1. Naredo E, et al. Validity, reproducibility, and responsiveness of a twelve-joint simplified power Doppler ultrasonographic assessment of joint inflammation in rheumatoid arthritis. Arthritis Care Res. 2008;59(4):515–22.

2. Backhaus M, et al. Evaluation of a novel 7-joint ultrasound score in daily rheumatologic practice: A pilot project. Arthritis Care Res. 2009;61(9):1194–201.

References

Disclosure of Interest None declared