title: The utility of three different methods for measuring urinary 18-hydroxycortisol in the differential diagnosis of suspected primary hyperaldosteronism.
abstract: OBJECTIVE
  Urine 18-hydroxycortisol (18-OHF) measurements are claimed to discriminate between primary hyperaldosteronism due to Conn's syndrome/adrenal adenoma or idiopathic bilateral adrenal hyperplasia (BAH), and also to identify cases of glucocorticoid-suppressible hyperaldosteronism (GSH). We have evaluated three urine 18-OHF methods using a panel of urine samples from patients with hypertension.
  
  
  METHODS
  Clinical methods comparative study.
  
  
  METHODS
  Urine samples from patients with primary hyperaldosteronism due to either adenoma (n = 6), BAH (n = 6), GSH (n = 9), or essential hypertension (n = 38) were analysed without knowledge of the diagnosis using three different methods in different laboratories. These included 'in-house' radioimmunoassay (RIA), 'in-house' time-resolved fluorometric assay (DELFIA), and gas chromatography mass spectrometry (GC-MS).
  
  
  RESULTS
  The three assays showed good correlation, but there were large bias differences: RIA bias was greater than DELFIA which was greater than GC-MS. Discrimination between adenoma and BAH patients was best for the DELFIA method, with no overlap between results for these two groups. All three methods gave significantly elevated results for the GSH group compared with the BAH and essential hypertension groups. No assay distinguished BAH from essential hypertension.
  
  
  CONCLUSIONS
  Measurement of urine 18-OHF may be a useful additional test in the differential diagnosis of primary hyperaldosteronism. The clinical diagnostic value of urinary 18-OHF measurements is method-dependent with the DELFIA assay having the best discriminatory value.
authors.affiliation: Endocrinology Unit, School of Molecular and Clinical Medicine, University of Edinburgh, Western General Hospital, Edinburgh EH4 2XU, UK. r.reynolds@ed.ac.uk
authors.forename: R M
authors.initials: RM
authors.lastname: Reynolds
authors.forename: L A
authors.initials: LA
authors.lastname: Shakerdi
authors.forename: K
authors.initials: K
authors.lastname: Sandhu
authors.forename: A M
authors.initials: AM
authors.lastname: Wallace
authors.forename: P J
authors.initials: PJ
authors.lastname: Wood
authors.forename: B R
authors.initials: BR
authors.lastname: Walker
mesh_terms: D000236:Adenoma / Q000652:urine; D000312:Adrenal Hyperplasia, Congenital / Q000652:urine; D003937:Diagnosis, Differential; D005470:Fluorometry / Q000379:methods; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods; D006801:Humans; D006854:Hydrocortisone / Q000031:analogs & derivatives* / Q000652:urine*; D006929:Hyperaldosteronism / Q000652:urine*; D006973:Hypertension / Q000652:urine; D011863:Radioimmunoassay / Q000379:methods; D011897:Random Allocation; D018709:Statistics, Nonparametric
chemical_list: C033689:18-hydroxycortisol; D006854:Hydrocortisone