title: Harmonisation of serum dihydrotestosterone analysis: establishment of an external quality assurance program.
abstract: BACKGROUND
  Serum dihydrotestosterone (DHT) is an important analyte for the clinical assessment of disorders of sex development. It is also reportedly a difficult analyte to measure. Currently, there are significant gaps in the standardisation of this analyte, including no external quality assurance (EQA) program available worldwide to allow for peer review performance of DHT. We therefore proposed to establish a pilot EQA program for serum DHT.
  
  
  METHODS
  DHT was assessed in the 2015 Royal College of Pathologists of Australasia Quality Assurance Programs' Endocrine program material. The material's target (i.e. "true") values were established using a measurement procedure based on isotope dilution gas chromatography (GC) tandem mass spectrometry (MS/MS). DHT calibrator values were based on weighed values of pure DHT material (>97.5% purity) from Sigma. The allowable limits of performance (ALP) were established as ±0.1 up to 0.5 nmol/L and ±15% for targets >0.5 nmol/L.
  
  
  RESULTS
  Target values for the six levels of RCPAQAP material for DHT ranged from 0.02 to 0.43 nmol/L (0.01-0.12 ng/mL). The material demonstrated linearity across the six levels. There were seven participating laboratories for this pilot study. Results of the liquid chromatography (LC) MS/MS methods were within the ALP; whereas the results from the immunoassay methods were consistently higher than the target values and outside the ALP.
  
  
  CONCLUSIONS
  This report provides the first peer comparison of serum DHT measured by mass spectrometry (MS) and immunoassay laboratories. Establishment of this program provides one of the pillars to achieve method harmonisation. This supports accurate clinical decisions where DHT measurement is required.
authors.forename: Ronda F
authors.initials: RF
authors.lastname: Greaves
authors.forename: Lisa
authors.initials: L
authors.lastname: Jolly
authors.forename: Michaela F
authors.initials: MF
authors.lastname: Hartmann
authors.forename: Chung Shun
authors.initials: CS
authors.lastname: Ho
authors.forename: Richard K T
authors.initials: RK
authors.lastname: Kam
authors.forename: John
authors.initials: J
authors.lastname: Joseph
authors.forename: Conchita
authors.initials: C
authors.lastname: Boyder
authors.forename: Stefan A
authors.initials: SA
authors.lastname: Wudy
mesh_terms: D002138:Calibration; D002853:Chromatography, Liquid / Q000592:standards; D013196:Dihydrotestosterone / Q000097:blood*; D004797:Enzyme-Linked Immunosorbent Assay / Q000592:standards; D008401:Gas Chromatography-Mass Spectrometry / Q000592:standards*; D006801:Humans; D007118:Immunoassay / Q000592:standards*; D007201:Indicator Dilution Techniques / Q000592:standards; D059021:Laboratory Proficiency Testing; D010865:Pilot Projects; D011786:Quality Control; D011863:Radioimmunoassay / Q000592:standards; D053719:Tandem Mass Spectrometry / Q000592:standards
chemical_list: D013196:Dihydrotestosterone