title: Accuracy-based proficiency testing for testosterone measurements with immunoassays and liquid chromatography-mass spectrometry.
abstract: BACKGROUND
  Accurate testosterone measurements are needed to correctly diagnose and treat patients. Proficiency Testing (PT) programs using modified specimens for testing can be limited because of matrix effects and usage of non-reference measurement procedure (RMP)-defined targets for evaluation. Accuracy-based PT can overcome such limitations; however, there is a lack of information on accuracy-based PT and feasibility of its implementation in evaluation for testosterone measurements.
  
  
  METHODS
  Unaltered, single-donor human serum from 2 male and 2 female adult donors were analyzed for testosterone by 142 NYSDH-certified clinical laboratories using 16 immunoassays and LC-MS/MS methods. Testosterone target values were determined using an RMP.
  
  
  RESULTS
  The testosterone target concentrations for the 4 specimens were 15.5, 30.0, 402 and 498ng/dl. The biases ranged from -17.8% to 73.1%, 3.1% to 21.3%, -24.8% to 8.6%, and -22.1% to 6.8% for the 4 specimens, respectively. Using a total error target of ±25.1%, which was calculated using the minimum allowable bias and imprecision, 73% of participating laboratories had ≥3 of the 4 results within these limits.
  
  
  CONCLUSIONS
  The variability in total testosterone measurements can affect clinical decisions. Accuracy-based PT can significantly contribute to improving testosterone testing by providing reliable data on accuracy in patient care to laboratories, assay manufacturers, and standardization programs.
authors.affiliation: Wadsworth Center, New York State Department of Health, Albany, NY, United States; College of Arts and Sciences, University at Albany, State University of New York, Albany, NY, United States.
authors.forename: Zhimin Tim
authors.initials: ZT
authors.lastname: Cao
authors.affiliation: Centers for Disease Control and Prevention, Atlanta, GA, United States.
authors.forename: Julianne Cook
authors.initials: JC
authors.lastname: Botelho
authors.affiliation: Wadsworth Center, New York State Department of Health, Albany, NY, United States; School of Public Health, University at Albany, State University of New York, Albany, NY, United States.
authors.forename: Robert
authors.initials: R
authors.lastname: Rej
authors.affiliation: Centers for Disease Control and Prevention, Atlanta, GA, United States. Electronic address: hvesper@cdc.gov.
authors.forename: Hubert
authors.initials: H
authors.lastname: Vesper
mesh_terms: D000328:Adult; D001774:Blood Chemical Analysis / Q000379:methods*; D002853:Chromatography, Liquid / Q000379:methods*; D005260:Female; D006801:Humans; D007118:Immunoassay / Q000379:methods*; D057230:Limit of Detection; D008297:Male; D013058:Mass Spectrometry / Q000379:methods*; D013739:Testosterone / Q000097:blood*
chemical_list: D013739:Testosterone
keywords: Accuracy; Proficiency Testing; Standardization; Testosterone