The aims of this study were to assess the prevalence of US-detected residual synovitis in patients with RA in clinical remission (CR) and evaluate its predictive value for relapse and structural progression.
We performed a systematic literature search of Medline, Embase and rheumatology meeting databases from 1 January 2001 to 28 May 2012. The prevalence of US grey-scale (USGS) signals (synovial hypertrophy or joint effusion) and power Doppler (PD) signals were collected, taking into account CR definitions [44-joint DAS (DAS44), 28-joint DAS (DAS28), SDAI, ACR 1981 or ACR/European League Against Rheumatism 2011], stage of RA (early or long-standing) and US examination (from 5 to 44 joints assessed). A meta-analysis assessing the risk of relapse or structural progression in patients with synovitis involved the Mantel-Haenszel method.
We included 19 studies of 1618 patients, 1369 in remission. The prevalence of USGS positive (USGS+), USGS+/PD negative (PD-), USGS+/PD positive (PD+) and USGS negative (USGS-/PD- was 84%, 41%, 44% and 15%, respectively. The prevalence of USGS+ or USGS+/PD+ was comparable among CR definitions and US methods. The prevalence of USGS+ and USGS+/PD+ was greater for long-standing than early RA (P < 0.001). Meta-analyses of five studies (271 patients), three studies (173 patients) and two studies (798 joints) revealed an association of USGS+/PD+ and risk of relapse [odds ratio (OR) 3.2 (95% CI 1.8, 5.9), P = 0.0001, I(2) = 0%] and structural progression in individual patients [OR 9.13 (95% CI 1.1, 74.3), P = 0.04, I(2) = 43%] and joints [OR 6.95 (95% CI 3.4, 13.9), P < 0.0001, I(2) = 6%] over 1-2 years.
US-detected residual synovitis is frequent and predicts the risk of relapse and structural progression in RA patients with CR.