Comment on "The effect of disease-modifying anti-rheumatic drugs on skeletal muscle mass in rheumatoid arthritis patients: a systematic review with meta-analysis".

We read with great interest the article by Hein et al., which described the meta-analysis study on the impact of disease-modifying anti-rheumatic drugs (DMARDs) therapy on skeletal muscle mass in rheumatoid arthritis (RA) patients. While the data presented are impressive, we add some remarks about methodological issues that should be considered. First, this meta-analysis does not include several necessary studies that have provided data on the relationship between anti-tumor necrosis factor (anti-TNF) therapy and body composition. To make the meta-analysis more comprehensive, it could be necessary to incorporate these studies into this analysis. Second, this study did not employ a representative measure of skeletal muscle mass that was adjusted for body size, such as skeletal muscle mass index (SMI). It is well recognized that skeletal muscle mass varies with body size, particularly height and body mass index. Given the heterogeneity background of body size in the studies included in this meta-analysis, it may be worthwhile to conduct an additional analysis regarding the associations between DMARDs and the adjusted measure of skeletal muscle mass such as SMI, which is recommended in several guidelines when determining and contrasting the quantity of skeletal muscle mass. Third, when determining body composition, several reports show variances between bioelectrical impedance analysis (BIA) and dual-energy X-ray absorptiometry (DEXA) in RA as well as in general. In this regard, it may not be appropriate to simultaneously perform a meta-analysis of skeletal muscle mass determined by DEXA and BIA. With the issues described above, we conclude by recommending additional investigations to strengthen the arguments presented by this valuable meta-analysis.