Antibodies to citrullinated peptides in tuberculosis
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BRIEF REPORT
Antibodies to citrullinated peptides in tuberculosis I. Lima & R. C. Oliveira & A. Atta & S. Marchi & L. Barbosa & E. Reis & M. G. Reis & M. B. Santiago
Received: 21 June 2012 / Revised: 13 December 2012 / Accepted: 11 January 2013 / Published online: 24 January 2013 # Clinical Rheumatology 2013
Abstract Rheumatoid arthritis (RA) is an autoimmune disease characterized by symmetric polyarthritis, rheumatoid factor (RF) positivity, and bone erosions. Recently, research has been conducted on anti-citrullinated peptide antibodies (ACPAs) to which there are greater sensitivity and specificity than RF. However, these antibodies have also been described in infectious diseases, particularly tuberculosis (TB), placing the high specificity of the test in doubt. The aim of this research was to study the prevalence of ACPAs in TB, RA, and healthy controls. Patients with bacteriologically confirmed pulmonary tuberculosis, RA (ACR criteria), in addition to healthy controls were included. ACPAs were researched by: anti-cyclic citrullinated peptide (CCP), anti-modified citrullinated vimentin (MCV), and RF by ELISA. The study was conducted in 50 TB patients, 50 with RA, and 20 controls. Anti-CCP antibodies were found in 39 (78 %) of the RA patients (median titer, 128 U), whereas antiMCV antibodies were found in 25 (50 %). Of the patients with TB, two (4 %) had positivity for antiCCP and anti-MCV and no patient in the control group tested positive for these antibodies. Sensitivity of antiI. Lima : M. B. Santiago Escola Bahiana de Medicina e Saúde Pública, Salvador, Bahia, Brazil R. C. Oliveira : A. Atta Faculdade de Farmácia da Universidade Federal da Bahia, Salvador, Brazil S. Marchi : L. Barbosa : E. Reis : M. G. Reis Fundação Oswaldo Cruz, Salvador, Brazil M. B. Santiago (*) Serviços Especializados em Reumatologia da Bahia, Rua Conde Filho 117, Graça, Salvador, Bahia CEP 40.150-150, Brazil e-mail: [email protected]
CCP for RA was 78 % (confidence interval (CI), 63 to 88 %) and specificity was 97 % (CI, 89 to 99 %) while the sensitivity of anti-MCV was 50 % (CI, 35–64 %) and specificity was 97 % (CI, 89 to 99 %). RF was positive in 40 samples (80 %) of RA, in 30 (60 %) of TB, and in 1 (5 %) of the controls. Our findings showed high sensitivity of anti-CCP and high specificity of both anti-CCP and anti-MCV antibodies for RA, even in a population with high incidence of tuberculosis. The higher frequency of positivity of ACPA in TB observed in previous studies may be attributed to methodological factors. Keywords ACPA . Anti-CCP . Anti-MCV . Rheumatoid arthritis . Rheumatoid factor . Tuberculosis
Introduction Rheumatoid arthritis (RA) is an autoimmune disease that affects around 1 % of the adult population [1]. In Brazil, its prevalence ranges from 0.2 to 1 % [2, 3]. The diagnosis of RA is based on clinical, radiological, and laboratory criteria [4, 5]. Advances in laboratory tests and in imagining exams made it possible to diagnosis RA at an earlier stage of the disease [6]. With respect to laboratory tests, research
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