Anti-CCP antibodies as a marker of rhupus
Sir,We have read with interest the works on rhupus, a clinical condition characterized by the coexistence of rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE), recently published in Lupus. 1,2 These publications prompted us to investigate the prevalence and characteristics of rhupus in our cohort of patients with SLE, 3,4 fulfilling international classification criteria. 5,6 This was a cross-sectional analytical study conducted in 377 Colombian patients with SLE and undertaken between February 1996 and June 2013. The patients' sociodemographic and cumulative clinical and laboratory data were obtained by interview, standardized report form, physical examination and chart review. The variables were registered at any time during the course of the disease as described elsewhere. 3,4 Likewise, the relevant laboratory variables associated with SLE were recorded. 3,4 All of the patients underwent antibodies determination, including IgM rheumatoid factor (RF) and IgG anti-cyclic citrullinated peptide (anti-CCP3), as described elsewhere. 3,4 Factors associated with rhupus were assessed by bivariate analysis and classification and regression trees (CART) analysis, with complex interactions not captured by logistic regression. The variables included in the statistical model were polyautoimmunity and multiple autoimmune syndrome, familial autoimmunity, gender, age at onset, smoking and coffee consumption, toxic exposure, comorbidities, cardiovascular disease, history of infections, malar rash, discoid rash, photosensitivity, oral ulcers, positive antinuclear antibody, arthritis, serositis, renal, neurologic, hematologic and immunologic disorder. 3,4 Likewise, positivity for antibodies, lupus anticoagulant and complement status were variables also included. The statistical analyses