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Ann Rheum Dis doi:10.1136/annrheumdis-2014-205428
  • Clinical and epidemiological research
  • Extended report

Additive effect of anti-citrullinated protein antibodies and rheumatoid factor on bone erosions in patients with RA

  1. Georg Schett1
  1. 1Department of Internal Medicine 3, University of Erlangen-Nuremberg, Erlangen, Germany
  2. 2Institute of Medical Physics, University of Erlangen-Nuremberg, Erlangen, Germany
  1. Correspondence to Georg Schett, Department of Internal Medicine 3, University of Erlangen-Nuremberg, Erlangen; Ulmenweg 18, Erlangen 91054, Germany; georg.schett{at}uk-erlangen.de
  • Received 17 February 2014
  • Revised 23 June 2014
  • Accepted 20 July 2014
  • Published Online First 12 August 2014

Abstract

Objective To determine whether there is an additive effect of anticitrullinated protein antibodies (ACPA) and rheumatoid factor (RF) on the number and size of bone erosions in patients with rheumatoid arthritis (RA)

Methods 242 patients with RA received high-resolution peripheral quantitative CT (HR-pQCT) scans of the metacarpophalangeal joints. Demographic and disease-specific parameters including ACPA and RF levels were recorded from all patients. Erosion numbers and their size were assessed in 238 patients at 714 individual joints (MCP 2, 3 and 4) and 5712 sites (each 4 quadrants in metacarpal heads and phalangeal bases). The volume of erosions was calculated by a semiellipsoid formula.

Results Of the 238 patients, 112 patients showed RF and ACPAs (ACPAs+RF+), 28 only RF (RF+), 29 only ACPAs (ACPA+) and 69 were antibody negative (NEG). Erosion number and size were highest in RF+ACPAs+ patient group with significant differences compared with NEG patients with respect to erosion number (p=0.001) and to ACPA-negative patients with respect to erosion size (p<0.001). Results maintained significance in a linear mixed model showing ACPAs+RF+ status and disease duration being associated with higher number (p=0.017 and p=0.005, respectively), and larger size (p=0.014 and p=0.013, respectively) of bone erosions. Furthermore, erosion size was influenced by the presence and titre of RF only in ACPA-positive patients with RA but not in ACPA-negative patients.

Conclusions ACPAs and RF show an additive effect on erosion number and erosion size. Concomitant presence of ACPAs and RF is associated with higher erosive disease burden in patients with RA. Furthermore, RF influences erosion size only in ACPA-positive but not in ACPA-negative patients.