title: Efficiency of a solid-phase chemiluminescence immunoassay for detection of antinuclear and cytoplasmic autoantibodies compared with gold standard immunoprecipitation.
abstract: OBJECTIVE
  The aim of this study was to compare the degree of agreement of a novel Zenit RA chemiluminescent immunoassay (CLIA) from A. Menarini Diagnostics (Florence, Italy) and the gold standard immunoprecipitation assay to screen for the presence of specific anti-U1snRNP, anti-Sm, anti-Ro/SS-A, anti-La/SS-B, anti-Jo-1((his)tRNA-Synthetase) and anti-Scl-70(Topo I) antibodies.
  
  
  METHODS
  We studied 114 sera, 98 from patients with well-defined autoimmune connective tissue diseases and 16 from blood donor volunteers. All samples were fully characterized using the new chemiluminescent immunoassay and immunoprecipitation. In addition, all the samples were analyzed by indirect immunofluorescence (IIF) and anti-Scl-70(Topo I) antibodies were analyzed by immunoblot (IB) assay. Discrepant samples were analyzed using a commercial dot blot technique (Recomline from Mikrogen). The simple Kappa coefficient was used to measure the level of agreement between the results of Zenit RA CLIA and the gold standard.
  
  
  RESULTS
  The Kappa agreement between Zenit RA CLIA and gold standard immunoprecipitation, as well as IB and IIFassays for the presence of anti-Scl-70(Topo I)(0.948) was excellent. The concordance between Zenit RA CLIA and gold standard immunoprecipitation for the presence of anti-U1snRNP (0.883), anti-Ro/SS-A (0.878), anti-Jo-1((his)tRNA-Synthetase) (0.791) and anti-Sm (0.786) was good, and excellent when the cut-off was raised to 14 U/ml (arbitrary units/ml). Between Zenit RA CLIA and gold standard immunoprecipitation for the presence of anti-La/SS-B, the Kappa agreement had a value of 0.689, but this improved to 0.775 when the cut-off was raised to14 U/ml. Precision was good based on the evaluation of replicate samples. Inter-assay coefficient variation was lower than 3.4 % (CV in %) in all the kits and <1.2 % (CV in  %) for intra-assay measurements.
  
  
  CONCLUSIONS
  Our findings show that Zenit RA CLIA was specific and sensitive to detect anti-U1snRNP, anti-Sm, anti-Ro/SS-A, anti-La/SS-B, anti-Jo-1((his)tRNA-Synthetase) and anti-Scl70(Topo I) autoantibodies. This simple, fast and precise method can be a suitable option to analyze these autoantibody specificities.
authors.affiliation: Department of Immunology, Hospital de la Santa Creu i Sant Pau, Avgda. S. Antoni Mª Claret 167, 08025 Barcelona, Spain ; Research Institute IBSantPau, Hospital de la Santa Creu i Sant Pau, Avgda. S. Antoni Mª Claret 167, 08025 Barcelona, Spain.
authors.forename: Carmen
authors.initials: C
authors.lastname: Gelpí
authors.affiliation: Department of Immunology, Hospital de la Santa Creu i Sant Pau, Avgda. S. Antoni Mª Claret 167, 08025 Barcelona, Spain.
authors.forename: Elena
authors.initials: E
authors.lastname: Pérez
authors.affiliation: Research Institute IBSantPau, Hospital de la Santa Creu i Sant Pau, Avgda. S. Antoni Mª Claret 167, 08025 Barcelona, Spain.
authors.forename: Cristina
authors.initials: C
authors.lastname: Roldan
keywords: Autoantibodies; ENA; Immunoprecipitation; Jo1(histRNA-synthetase); La/SS-B; Ro/SS-A; Scl-70(Topo-I); Sensitivity; Sm; Specificity; U1snRNP; Zenit RA chemiluminescent immunoassay