The relationship between US7 ultrasound joint scoring system and disease activity score DAS28 in rheumatoid arthritis: A study in Indian population

Abstract

Introduction: US7 (7 joint ultrasound score) is an emerging ultrasound (US) joint scoring system for the assessment of disease activity in patients with Rheumatoid Arthritis (RA). Methods and Material: The study was conducted at a tertiary care center in Southern India. Sixty-two patients of RA were recruited for this cross-sectional observational study. Patients' clinical & laboratory parameters were used to calculate the disease activity score DAS28. Grayscale and Power Doppler Ultrasound (GSUS & PDUS) were performed to calculate US7 score.Statistical analysis used: Spearman's rank-order correlation, Pearson interclass correlation and ROC (receiver operating characteristic) curve analysis were performed. Results: Median DAS28 value was 4.04 with one patient in clinical remission. There was a statistically significant positive correlation (r=0.262) between synovitis by GSUS score & DAS 28 (p-value = 0.040) and synovitis by PDUS score and DAS 28 (r=0.340, p-value = 0.004). No significant correlation was found between DAS28 and tenosynovitis or erosions score. ROC curve analysis yielded the p values of 0.04 and 0.004 for synovitis by GSUS and synovitis by PDUS respectively in differentiating between the patients with low (DAS groups 1 & 2) and high disease activity (3 & 4). Conclusions: There is good correlation of the synovitis component of US7 score with DAS28. However, relationship of tenosynovitis and erosions with disease activity is questionable according to our results. An 'abbreviated US7' score with detection of only synovitis may be more suitable. This requires further validation.