title: Diagnostic Performance of an Anti-Actin Autoantibody Binding Enzyme Immunodot Blot in Autoimmune Hepatitis Type 1.
abstract: BACKGROUND
  A serologic hallmark of autoimmune hepatitis (AIH) type 1 are anti-smooth muscle autoantibodies (ASMA) with specificity for filamentous actin (F-actin; AAA (anti-actin antibodies)), traditionally detected by indirect immunofluorescence (IFT) using rat liver, kidney, and stomach tissue sections as substrates. However, IFT is a subjective method requiring an experienced investigator. Therefore, a more objective technique for the detection of AAA may be a helpful diagnostic tool.
  
  
  METHODS
  In a retrospective study with cross-sectional design, we evaluated AAA detected by an enzyme immunodot blot (IDB; Liver5 IgG BlueDot, D-tek, Mons, Belgium). Serum samples of patients with AIH type 1 (n = 47) and specified controls (n = 142) were included. For comparison, standard IFT was applied to rat LKS (liver, kidney, stomach) triple tissue sections.
  
  
  RESULTS
  IDB readings were done by two independent investigators (92% concordance). The diagnostic sensitivity of the AAA-IDB was 70%, compared to 51% of AAA-IFT (n.s.). The diagnostic specificity of AAA-IDB was significantly lower compared to AAA-IFT (76% vs. 94%; P < 0.0005). Correspondingly, the positive predictive value (49% vs. 75%; P < 0.05) and positive likelihood ratio (2.9 vs. 8.5) differed significantly. Neither prescreening for ANA or ASMA, nor the exclusion of infectious hepatopathies resulted in a significantly better diagnostic performance of the IDB.
  
  
  CONCLUSIONS
  Compared to standard IFT, testing for AAA via IDB did not result in a significantly better diagnostic performance for AIH type 1. A blot with higher antigen binding specificity may be more functional.
authors.affiliation: Niels-Stensen-Kliniken, Osnabrück, Germany.
authors.forename: Heiko
authors.initials: H
authors.lastname: Schotte
authors.affiliation: Medizinische Klinik und Poliklinik D, Universitätsklinikum Münster, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Willeke
authors.affiliation: Centrum für Laboratoriumsmedizin, Universitätsklinikum Münster, Germany.
authors.forename: Johanna
authors.initials: J
authors.lastname: Schmalhorst
authors.affiliation: Centrum für Laboratoriumsmedizin, Universitätsklinikum Münster, Germany.
authors.forename: Bernhard
authors.initials: B
authors.lastname: Schlüter
mesh_terms: D000199:Actins / Q000276:immunology*; D000293:Adolescent; D000328:Adult; D000368:Aged; D001323:Autoantibodies / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D005260:Female; D019084:Fluorescent Antibody Technique, Indirect; D019693:Hepatitis, Autoimmune / Q000175:diagnosis* / Q000276:immunology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D012015:Reference Standards
chemical_list: D000199:Actins; D001323:Autoantibodies
keywords: anti-actin autoantibodies; autoimmune hepatitis type 1; enzyme immunodot blot