The role of musculoskeletal ultrasound in difficult-to-treat RA: Insights from a systematic literature review

: Difficult-to-treat rheumatoid arthritis (D2TRA) identifies patients with insufficient response to biological or targeted-synthetic disease-modifying drugs (b/ts DMARDs), heralding a more severe phenotype. Musculoskeletal ultrasound (MSK-US) provides information on MSK inflammatory load and damage, being widely used in RA and inflammatory arthritides, yet the US patterns of D2TRA and correlation with clinical parameters have not been unanimously described so far. Here we investigated MSK-US patterns and their prognostic value in D2TRA through a systematic literature review (SLR) across MEDLINE (through PubMed), Scopus and Ovid (Embase) electronic databases. We initially retrieved 2365 papers; following the application of appropriate strings the number was lowered to 22. Among those, three papers fulfilled the required criteria. A total of 159 patients with D2TRA were analyzed. In comparison to non-D2TRA, D2TRA patients exhibited more extensive and severe synovitis, which correlated with higher disease activity scores and poorer treatment outcomes. Most US-affected joints belonged to hand and wrist. Grey-scale (GS) rather than power-Doppler (PD) synovitis score was consistently increased across D2TRA joints. Inclusion of US in recognition of D2TRA decreased the proportion of classifiable patients, identifying the true inflammatory D2T cases. The results of this SLR suggest that standardization of US phenotyping may aid the identification and stratification of D2TRA patients in clinical practice.