title: Measuring adrenal autoantibody response: interlaboratory concordance in the first international serum exchange for the determination of 21-hydroxylase autoantibodies.
abstract: 21-hydroxylase autoantibodies (21OHAb) are the gold standard immune marker to identify patients with clinical or subclinical autoimmune Addison's disease (AAD). No assessment of interlaboratory concordance has been made for 21OHAb measurement. Serum samples from 267 patients with primary adrenal insufficiency and from 83 healthy control subjects were distributed to four independent laboratories that determined presence and titer of 21OHAb, by using radiobinding assays with either in vitro translated 35S-radiolabelled or 125I-radiolabelled autoantigen. Cohen's κ of inter-rater agreement ranged from 0.857 to 0.983, showing a very good concordance of the positive/negative score among the four laboratories. Passing-Bablok regression showed a good agreement of 21OHAb titers arranged by ranks, but important discrepancies emerged at the Bland-Altman plot, as the repeatability coefficient was much higher than the laboratory cut-offs, which indicates that results from different laboratories cannot be used interchangeably. A standardization international program for 21OHAb measurement is strongly needed.
authors.affiliation: Department of Internal Medicine, Section of Internal Medicine and Endocrine & Metabolic Sciences, University of Perugia, 06126 Perugia, Italy. alberto.falorni@unipg.it
authors.forename: Alberto
authors.initials: A
authors.lastname: Falorni
authors.forename: Shu
authors.initials: S
authors.lastname: Chen
authors.forename: Renato
authors.initials: R
authors.lastname: Zanchetta
authors.forename: Liping
authors.initials: L
authors.lastname: Yu
authors.forename: Claudio
authors.initials: C
authors.lastname: Tiberti
authors.forename: Maria Luisa
authors.initials: ML
authors.lastname: Bacosi
authors.forename: Jadwiga
authors.initials: J
authors.lastname: Furmaniak
authors.forename: Vittorio
authors.initials: V
authors.lastname: Bini
authors.forename: Francesco
authors.initials: F
authors.lastname: Dotta
authors.forename: George S
authors.initials: GS
authors.lastname: Eisenbarth
authors.forename: Bernard Rees
authors.initials: BR
authors.lastname: Smith
authors.forename: Corrado
authors.initials: C
authors.lastname: Betterle
mesh_terms: D000224:Addison Disease / Q000097:blood / Q000175:diagnosis* / Q000276:immunology; D000328:Adult; D000917:Antibody Formation; D001323:Autoantibodies / Q000097:blood* / Q000276:immunology; D015415:Biomarkers / Q000097:blood; D005260:Female; D006801:Humans; D007755:Laboratories, Hospital; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011863:Radioimmunoassay / Q000592:standards; D015203:Reproducibility of Results; D013255:Steroid 21-Hydroxylase / Q000276:immunology*; D055815:Young Adult
chemical_list: D001323:Autoantibodies; D015415:Biomarkers; D013255:Steroid 21-Hydroxylase