title: Performance characteristics of a new automated method for measurement of anti-cyclic citrullinated peptide.
abstract: BACKGROUND
  Rheumatoid arthritis (RA) is a chronic inflammatory auto-immune disease affecting approximately 1%-2% of the population worldwide. RA is a potentially crippling disease since it results in malformation of the joints. RA is mostly diagnosed based on clinical manifestations but serological tests against autoantibodies, such as rheumatoid factor and anti-cyclic citrullinated peptides (aCCP), are available. The presence of aCCP antibodies is strongly associated with a more severe, destructive disease course. Recently, a new test for the measurement of aCCP antibodies on the IMMULITE 2000(XPi) platform was developed by Siemens Healthcare. In this study we investigated the performance characteristics of this new aCCP test in four different hospital laboratories and compared the new test with three different commercially available platforms.
  
  
  METHODS
  Samples were collected from patients presented to the hospital for aCCP measurement. Serum aCCP levels were determined by aCCP (Ig)G assay for IMMULITE 2000(XPi) systems (Siemens Healthcare), ImmunoScan RA enzyme-linked immunosorbent assay (ELISA) test (Eurodiagnostica), Immunocap 250 (Thermofisher) or aCCP IgG assay on the Modular system (Roche Diagnostics). The evaluation protocol consisted of within-run imprecision (20 sequential runs), between-run imprecision (16 workdays), comparison of serum and plasma measurement and method comparison.
  
  
  RESULTS
  The within-run imprecision (n=20) for aCCP IgG assay on three different IMMULITE 2000(XPi) systems ranged from 3.0% to 6.9% at levels 3.2-171.2 U/mL. Between-run imprecision (n=16 days) ranged from 5.2% to 11% at levels of 3.2-106.9 U/mL. Method comparison showed good correlation when samples were measured on two different Immulite analyzers in two different hospital laboratories [0.21+0.96x (n=40)]. Method comparison of the IMMULITE 2000(XPi) aCCP test with aCCP on Immunoscan RA ELISA (n=112), Immunocap 250 (n=105) and the Modular system (n=289) resulted in a concordance of 90.2%, 93.3% and 94.8%, respectively. Correlation of serum versus heparin samples showed a correlation of 0.12+1.08x for the Immulite 2000(XPi) test.
  
  
  CONCLUSIONS
  The aCCP assay on the IMMULITE 2000(XPi) has good performance characteristics and shows high level of concordance with the aCCP test on Immunoscan RA ELISA test, Immunocap 250 and the Modular systems.
authors.forename: Madelon
authors.initials: M
authors.lastname: Noordegraaf
authors.forename: Albert
authors.initials: A
authors.lastname: Wolthuis
authors.forename: Frans
authors.initials: F
authors.lastname: Peters
authors.forename: Monique
authors.initials: M
authors.lastname: de Groot
authors.forename: Rein
authors.initials: R
authors.lastname: Hoedemakers
mesh_terms: D001323:Autoantibodies / Q000097:blood* / Q000276:immunology; D001331:Automation; D001774:Blood Chemical Analysis / Q000379:methods*; D006493:Heparin / Q000378:metabolism; D006801:Humans; D007755:Laboratories, Hospital; D010456:Peptides, Cyclic / Q000276:immunology*
chemical_list: D001323:Autoantibodies; D010456:Peptides, Cyclic; C487763:cyclic citrullinated peptide; D006493:Heparin