title: Production, analysis, and characterization of reference materials for prostate-specific antigen.
abstract: OBJECTIVE
  To produce a set of three reference materials that mimic sera from patients with prostate disorders in the prostate-specific antigen (PSA) concentration range important for clinical screening for prostate cancer (approximately 0.5, approximately 4.0, and approximately 10.0 ng/mL), to analyze these reference materials in a large number of clinical laboratories using a variety of commercially available methods, and to characterize the molecular forms of PSA in them.
  
  
  METHODS
  Units of serum from healthy individuals and from patients with varying degrees of elevated PSA were pooled, lyophilized, and distributed along with conventionally prepared, semen-supplemented proficiency testing samples to laboratories participating in the College of American Pathologists Basic Ligand Survey. The reference material and one of the standard Survey samples were fractionated by Sephacryl S-200-HR gel filtration chromatography.
  
  
  RESULTS
  The Abbott IMx, Hybritech Tandem-E, Hybritech Tandem-R, and Tosoh AIA-Pack all measured PSA in the reference material fairly equally (agreement within +/- 12%). In contrast, the Abbott IMx results in the semen-supplemented Survey specimens were as much as 1.8-fold higher than the other three assays. Characterization of the molecular forms showed the reference material was approximately 90% alpha 1-antichymotrypsin-bound PSA, whereas the semen-supplemented Survey specimens were approximately 40% alpha 1-antichymotrypsin-bound PSA, which largely explained the difference in assay recoveries.
  
  
  CONCLUSIONS
  Semen-free materials containing only endogenous PSA much more closely mimic real clinical specimens and should prove useful in efforts to standardize clinical PSA assays.
authors.affiliation: Department of Laboratory Medicine and Pathology, University of Minnesota, Minneapolis, USA.
authors.forename: U C
authors.initials: UC
authors.lastname: Garg
authors.forename: J H
authors.initials: JH
authors.lastname: Howanitz
authors.forename: R M
authors.initials: RM
authors.lastname: Nakamura
authors.forename: R H
authors.initials: RH
authors.lastname: Plous
authors.forename: J H
authors.initials: JH
authors.lastname: Eckfeldt
mesh_terms: D001769:Blood / Q000276:immunology; D002850:Chromatography, Gel; D006801:Humans; D007118:Immunoassay; D008297:Male; D017430:Prostate-Specific Antigen / Q000032:analysis / Q000302:isolation & purification / Q000592:standards*; D011471:Prostatic Neoplasms / Q000175:diagnosis; D012015:Reference Standards; D012661:Semen / Q000276:immunology; D000514:alpha 1-Antichymotrypsin / Q000032:analysis
chemical_list: D000514:alpha 1-Antichymotrypsin; D017430:Prostate-Specific Antigen