title: Prevalence, sensitivity and specificity of antibodies against carbamylated proteins in a monocentric cohort of patients with rheumatoid arthritis and other autoimmune rheumatic diseases.
abstract: Antibodies against carbamylated proteins (anti-CarP) have been recently identified in the sera of patients with rheumatoid arthritis (RA). The objective of the study was to evaluate the prevalence, sensitivity and specificity of anti-CarP compared to anti-citrullinated peptide antibodies (ACPA) and rheumatoid factor (RF), replicating the existing data in a large cohort of Italian patients with RA and extending the evaluation to other autoimmune rheumatic diseases (AIRDs).
  
  
  
  Serum samples (n = 607) from 309 patients with RA, 200 disease controls and 98 normal healthy subjects (NHS) were evaluated. Anti-CarP were detected using carbamylated fetal calf serum as the antigen. ACPAs were detected using second-generation ELISA and IgM RF was assessed as part of routine analysis.
  
  
  
  Anti-CarP antibodies were detected in 117 patients with RA (34.4%), ACPA in 190 patients (61.4%) and RF in 202 patients (65.3%). Two (2.04%) of the NHS were positive for anti-CarP, one NHS (1.02%) was positive for ACPA and three NHS were positive for RF (3.06%). Among disease controls, anti-CarP antibodies were detected in 33 patients (16.5%), ACPA in 29 patients (14.5%) and RF in 64 patients (32%). In particular, 16.8% of patients with systemic lupus erythematosus and 31.1% of patients with Sjögren syndrome were positive for anti-CarP. The sensitivity of anti-CarP, ACPA and RF was 46.8%, 61.8% and 64.4%, respectively and specificity was 91.95%, 89.93% and 76.51%, respectively.
  
  
  
  The present study extends the knowledge of anti-CarP antibodies, confirming previous data on the diagnostic accuracy of anti-CarP in RA in a large cohort of Italian patients. Anti-CarP antibodies demonstrated relatively low sensitivity and slightly higher specificity compared to ACPA and RF. Even if predominantly present in RA, anti-CarP was detected in a variable percentage of patients with other autoimmune rheumatic diseases and their generation could be attributed to the inflammatory status; the clinical relevance of anti-CarP antibodies in these latter patients should be further determined.
authors.affiliation: Dipartimento di Medicina Interna e Specialità Mediche, Reumatologia, Sapienza Università di Roma, Rome, Italy.
authors.forename: Arbi
authors.initials: A
authors.lastname: Pecani
authors.affiliation: Dipartimento di Medicina Interna e Specialità Mediche, Reumatologia, Sapienza Università di Roma, Rome, Italy. cristiano.alessandri@uniroma1.it.
authors.forename: Cristiano
authors.initials: C
authors.lastname: Alessandri
authors.affiliation: Dipartimento di Medicina Interna e Specialità Mediche, Reumatologia, Sapienza Università di Roma, Rome, Italy.
authors.forename: Francesca Romana
authors.initials: FR
authors.lastname: Spinelli
authors.affiliation: Dipartimento di Medicina Interna e Specialità Mediche, Reumatologia, Sapienza Università di Roma, Rome, Italy.
authors.forename: Roberta
authors.initials: R
authors.lastname: Priori
authors.affiliation: Dipartimento di Medicina Interna e Specialità Mediche, Reumatologia, Sapienza Università di Roma, Rome, Italy.
authors.forename: Valeria
authors.initials: V
authors.lastname: Riccieri
authors.affiliation: Dipartimento di Medicina Interna e Specialità Mediche, Reumatologia, Sapienza Università di Roma, Rome, Italy.
authors.forename: Manuela
authors.initials: M
authors.lastname: Di Franco
authors.affiliation: Dipartimento di Medicina Interna e Specialità Mediche, Reumatologia, Sapienza Università di Roma, Rome, Italy.
authors.forename: Fulvia
authors.initials: F
authors.lastname: Ceccarelli
authors.affiliation: Dipartimento di Medicina Interna e Specialità Mediche, Reumatologia, Sapienza Università di Roma, Rome, Italy.
authors.forename: Tania
authors.initials: T
authors.lastname: Colasanti
authors.affiliation: Dipartimento di Medicina Interna e Specialità Mediche, Reumatologia, Sapienza Università di Roma, Rome, Italy.
authors.forename: Monica
authors.initials: M
authors.lastname: Pendolino
authors.affiliation: Dipartimento di Medicina Interna e Specialità Mediche, Reumatologia, Sapienza Università di Roma, Rome, Italy.
authors.forename: Riccardo
authors.initials: R
authors.lastname: Mancini
authors.affiliation: Dipartimento di Medicina Interna e Specialità Mediche, Reumatologia, Sapienza Università di Roma, Rome, Italy.
authors.forename: Simona
authors.initials: S
authors.lastname: Truglia
authors.affiliation: Dipartimento di Medicina Interna e Specialità Mediche, Reumatologia, Sapienza Università di Roma, Rome, Italy.
authors.forename: Cristiana
authors.initials: C
authors.lastname: Barbati
authors.affiliation: Dipartimento di Medicina Interna e Specialità Mediche, Reumatologia, Sapienza Università di Roma, Rome, Italy.
authors.forename: Marta
authors.initials: M
authors.lastname: Vomero
authors.affiliation: Dipartimento di Medicina Interna e Specialità Mediche, Reumatologia, Sapienza Università di Roma, Rome, Italy.
authors.forename: Danilo
authors.initials: D
authors.lastname: Sabatinelli
authors.affiliation: Dipartimento di Medicina Interna e Specialità Mediche, Reumatologia, Sapienza Università di Roma, Rome, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Morello
authors.affiliation: Dipartimento di Medicina Interna e Specialità Mediche, Reumatologia, Sapienza Università di Roma, Rome, Italy.
authors.forename: Guido
authors.initials: G
authors.lastname: Valesini
authors.affiliation: Dipartimento di Medicina Interna e Specialità Mediche, Reumatologia, Sapienza Università di Roma, Rome, Italy.
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Conti
mesh_terms: D000328:Adult; D000368:Aged; D019540:Area Under Curve; D001172:Arthritis, Rheumatoid / Q000175:diagnosis* / Q000276:immunology*; D001323:Autoantibodies / Q000097:blood / Q000276:immunology*; D001324:Autoantigens / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012372:ROC Curve; D012216:Rheumatic Diseases / Q000175:diagnosis / Q000276:immunology; D012680:Sensitivity and Specificity
chemical_list: D001323:Autoantibodies; D001324:Autoantigens
keywords: Anti-carbamylated proteins antibodies; Anti-citrullinated peptides antibodies; Autoimmune rheumatic diseases; Rheumatoid arthritis; Rheumatoid factor; Sjögren syndrome post-translational modifications; Systemic lupus erythematosus