title: Solid phase competitive luminescence immunoassay for immunoglobulin A in faeces: development and clinical validation.
abstract: We describe a new simple solid-phase competitive luminescence immunoassay (LIA) for the determination of immunoglobulin A (IgA) in faeces. The assay utilizes an anti-alpha-chain IgA antibody which is coated to polystyrene beads and acridinium ester-labelled human IgA as tracer and, therefore, measures both monomeric and polymeric IgA. Dilution recovery of an internal standard was 96, 100 and 103%. Interassay and intra-assay coefficients of variation (C.V.) ranged from 4.5 to 12.9%. The upper limit of normal of faecal IgA in 122 healthy controls was found to be 300 mg/l IgA (mean 73 mg/l, specificity of 99.2%). Patients with inactive Crohn's disease (Crohn's disease activity index (CDAI < 150, n = 14) had faecal IgA values up to 3317 mg/l (mean 1073 mg/l; P < 0.0001). In the active group (CDAI > 150, n = 26) faecal IgA values ranged from 49 to 4094 mg/l (mean 1253 mg/l; P < 0.0001). Patients with ulcerative colitis were divided into a group with active disease (n = 18) and a remission group (n = 16) with values up to 1843 mg/l faecal IgA (man 486 mg/l; P < 0.0032) and up to 602 mg/l faecal IgA (mean 176 mg/l; P < 0.4833), respectively. We also studied patients with non-inflammatory diseases of the gut with this assay. This LIA has proved to be a reliable method for the determination of elevated faecal IgA concentrations and for the detection of pathological findings in the gastrointestinal tract, especially in Crohn's disease.
authors.affiliation: Department of Endocrinology and Oncology, Laboratory Group, Heidelberg, Germany.
authors.forename: E
authors.initials: E
authors.lastname: Schoof
authors.forename: M R
authors.initials: MR
authors.lastname: John
authors.forename: B
authors.initials: B
authors.lastname: Arndt
authors.forename: P
authors.initials: P
authors.lastname: Gao
authors.forename: D
authors.initials: D
authors.lastname: Theuer
authors.forename: A
authors.initials: A
authors.lastname: Sieg
authors.forename: H
authors.initials: H
authors.lastname: Schmidt-Gayk
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001667:Binding, Competitive; D003093:Colitis, Ulcerative / Q000276:immunology; D003111:Colonic Polyps / Q000276:immunology; D015179:Colorectal Neoplasms / Q000737:chemistry / Q000276:immunology; D003424:Crohn Disease / Q000276:immunology; D004240:Diverticulum / Q000276:immunology; D005243:Feces / Q000737:chemistry*; D006484:Hemorrhoids / Q000276:immunology; D006801:Humans; D007118:Immunoassay / Q000379:methods* / Q000706:statistics & numerical data; D007070:Immunoglobulin A / Q000737:chemistry*; D008163:Luminescent Measurements; D008875:Middle Aged; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D007070:Immunoglobulin A