Background Joint involvement represents one of the most frequent manifestations in Systemic Lupus Erythematosus (SLE) patients (incidence 69–95%), with different degrees of severity. Currently, there are no validated indices to evaluate joint involvement in SLE. Musculo-skeletal ultrasonography (US) has been widely applied in patients affected by different arthropathies. US-detected synovitis reflects the inflammatory state at the joint level, as demonstrated by the correlation with histological modifications. Furthermore, US-synovitis significantly correlated with disease activity indices, such as DAS28.
Objectives In the present study, we aimed at assessing a correlation between the composite indices DAS28 (Disease Activity Score 28), CDAI (Clinical Disease Activity Index), SDAI (Simplified Disease Activity Index), STR (Swollen to Tender Ratio) and the US-detected synovitis in a cohort of SLE patients with joint involvement.
Methods One hundred seven patients (M/F 7/100, mean age ±SD 48.4±13.8 years, mean disease duration ±SD 156.0±129.6 months) with at least one tender joint were enrolled. We registered the number of swollen and tender joint count (0–28) and the patient's/physician's disease activity on visual analogue scale (0–100). DAS28-ESR, CDAI, SDAI and STR were calculated. The US evaluation of 12 joints (I-V metacarpophalangeal, I-V proximal interphalangeal, wrist and knee bilateral) was performed to identify inflammatory features (synovial effusion, synovial hypertrophy and power Doppler) according with OMERACT definitions. These elementary lesions were scored according to a semi-quantitative scale (0 = absent, 1 = mild, 2 = moderate and 3 = severe). The sum of the semi-quantitative scores allows obtaining a total score of the patient's inflammatory state (0–216).
Results As reported in Figure 1, by using the Spearman analysis, a positive correlation between US-score and SDAI (r=0.33, P=0.02), CDAI (r=0.29, P=0.03) and STR (r=0.42, P=0.0005) was identified. In particular, SLE patients with high disease activity according with STR value (>1) showed a higher US score (16.3±19.3) in comparison with moderate (7.7±4.5, P=NS) or low disease activity (7.1±7.9, P=0.02). Moreover, US score resulted significantly lower in patients with DAS28 remission compared to those with an active disease (4.5±4.4 versus 7.05±5.1, P=0.03; Mann-Whitney test).
Conclusions We analyzed a large SLE cohort with articular involvement identifying a significant correlation between US scoreand the composite indices CDAI, SDAI and STR. Furthermore, US-score may be able to discriminate DAS28-remission patients. Taken together, these results suggest the ability of composite indices in detecting the joint activity in SLE patients and the possibility to use them in clinical practice to assess this frequent and potentially disabling manifestation.
Disclosure of Interest None declared