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With interest we read the article by Hecht et al1 who studied the associations of anticitrullinated peptide antibodies (ACPA) and rheumatoid factor (RF) with bone erosions in rheumatoid arthritis (RA). The background of this study was that ACPAs directed against citrullinated vimentin induce differentiation of osteoclasts, indicating that ACPA has a direct effect on bone resorption.2 No biological data are available on whether RF also affects bone cells and, given the overlap between ACPA-positivity and RF-positivity, the authors wanted to distinguish the association between RF and bone erosions from the association between ACPA and bone erosions. In a cross-sectional study, high-resolution peripheral quantitative CT (HR-pQCT) images of metacarpophalangeal (MCP) 2–4 joints of 238 patients with RA were made and groups of patients with different combinations of autoantibodies were compared. The authors observed mainly differences in erosive burden in patients with both antibodies compared with those without antibodies. In a subgroup analysis, they also reported a higher erosive burden in ACPA+/RF+ patients compared with ACPA+/RF− patients. Based on their findings the authors suggested that RF may act as an enhancer of bone loss in ACPA-positive patients.
HR-pQCT is an interesting tool that admits …