title: [Analysis of an iodide radioimmunoassay for 11-deoxicortisol measurement].
abstract: OBJECTIVE
  Our aim was to correlate 11-deoxycortisol levels obtained by two currently available techniques for 11-deoxycortisol measurement: radioimmunoassay, and high performance liquid chromatography followed by tandem mass spectrometry (MS/MS). The latter is the gold standard method for steroid hormone measurement.
  
  
  METHODS
  We selected 88 samples and the results of these two methods were compared by Deming regression.
  
  
  RESULTS
  The analytical sensitivity of the RIA was 0.30 ng/mL, with inadequate linearity and inadequate precision profile (34% of the samples had a CV ≥ 20%). From the selected samples, 54 had measurable levels of 11-deoxycortisol in both methods and were used in the comparison. The comparison of RIA with LC-MS/MS showed an overestimation of the results by RIA. The correlation coefficient was 0.610; linear regression slope was 3.751; and the intercept was 0.145, indicating a poor correlation between the two methods.
  
  
  CONCLUSIONS
  We concluded that 11-deoxycortisol measured by radioimmunoassay, despite a good analytical sensitivity, showed very low specificity, precluding its use as a reliable method for 11-deoxycortisol measurement.
authors.affiliation: Laboratório de Hormônios e Genética Molecular (LIM/42), Hospital das Clínicas, Faculdade de Medicina, Universidade de São Paulo, São Paulo, SP, Brasil.
authors.forename: João Luiz de Oliveira
authors.initials: JL
authors.lastname: Madeira
authors.affiliation: Laboratório de Hormônios e Genética Molecular (LIM/42), Hospital das Clínicas, Faculdade de Medicina, Universidade de São Paulo, São Paulo, SP, Brasil.
authors.forename: Luciane Zgoda
authors.initials: LZ
authors.lastname: Bussmann
authors.affiliation: Laboratório de Hormônios e Genética Molecular (LIM/42), Hospital das Clínicas, Faculdade de Medicina, Universidade de São Paulo, São Paulo, SP, Brasil.
authors.forename: Helena Panteliou
authors.initials: HP
authors.lastname: Lima-Valassi
authors.affiliation: Laboratório de Hormônios e Genética Molecular (LIM/42), Hospital das Clínicas, Faculdade de Medicina, Universidade de São Paulo, São Paulo, SP, Brasil.
authors.forename: Berenice Bilharinho de
authors.initials: BB
authors.lastname: Mendonça
mesh_terms: D019326:17-alpha-Hydroxyprogesterone / Q000032:analysis; D000312:Adrenal Hyperplasia, Congenital / Q000175:diagnosis*; D015982:Bias; D015415:Biomarkers / Q000097:blood; D002851:Chromatography, High Pressure Liquid; D003350:Cortodoxone / Q000097:blood*; D006801:Humans; D007457:Iodine Radioisotopes; D011863:Radioimmunoassay / Q000379:methods; D011933:Reagent Kits, Diagnostic / Q000592:standards*; D012015:Reference Standards; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D053719:Tandem Mass Spectrometry
chemical_list: D015415:Biomarkers; D007457:Iodine Radioisotopes; D011933:Reagent Kits, Diagnostic; D019326:17-alpha-Hydroxyprogesterone; D003350:Cortodoxone