Background Anti-citrullinated protein antibodies (ACPA) are known to be associated with joint destruction and a more severe disease course in rheumatoid arthritis (RA) patients. Recently, ACPA have been identified to directly induce bone loss .
Objectives To investigate the influence of ACPAs on periarticular bone structure in RA-patients using high-resolution imaging of bone.
Methods 242 RA-patients fulfilling the new ACR/EULAR-criteria received high-resolution peripheral quantitative computed tomography (HR-pQCT) of the 2nd-4th metacarpophalangeal joints of the dominant hand. Age, gender, disease activity (DAS28), disease duration, rheumatoid factor (RF), ACPA (by anti-CCP2 ELISA), and anti-rheumatic therapy were recorded. Number, width, depth and volume of erosions were assessed by 2 independent readers unaware of patients characteristics. For calculation of erosion volumes, a semi-ellipsoid formula was used .
Results 104 patients were RF+/CCP+, 27 RF+/CCP-, 28 RF-/CCP+ and 68 RF-/CCP-. All groups were comparable for age, gender, disease activity, disease duration and anti-rheumatic therapy. 15 patients were excluded due to movement artefacts. The RF-/ACPA+ and the RF+/ACPA+ groups had significantly (p <0.001) larger erosions compared to the RF+/ACPA- and RF-/ACPA- groups. Interestingly, erosions in the RF-/ACPA+ group were even larger than in the RF+/ACPA+ group (p <0.001). Inter-observer reliability (SF, CH) for erosion numbers, widths, depths and volumes was high (mean ICCs: 0.988, 0.977, 0.933, 0.970 and 0,961).
Conclusions ACPA-positivity is associated with larger bone erosions in RA-patients. Thus, ACPA essentially contribute to bone loss in RA by enhancing osteoclast activity, which is the key prerequisite for bone erosion. Moreover, ACPA impacts bone erosion independently from presence or absence of RF.
Harre U, Georgess D, Bang H, et al. Induction of osteoclastogenesis and bone loss by human autoantibodies against citrullinated vimentin. The Journal of clinical investigation. 2012 May 1; 122(5):1791-1802.
Albrecht A, Finzel S, Englbrecht M, et al. The structural basis of MRI bone erosions: an assessment by microCT. Annals of the rheumatic diseases. 2012 Sep 19.
Disclosure of Interest None Declared
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