title: Nucleic acid detection immunoassay for prostate-specific antigen based on immuno-PCR methodology.
abstract: BACKGROUND
  Serum prostate-specific antigen (PSA) concentrations after radical prostatectomy typically become undetectable with the use of current immunometric assay methods. Despite modern surgical techniques, 15%-30% of prostate cancer patients undergoing radical prostatectomy develop a biochemical recurrence during follow-up. Unfortunately, poor analytical sensitivity of standard PSA assays delays biochemical recurrence detection, and because of day-to-day assay imprecision ultrasensitive PSA assays cannot assess PSA kinetics. We developed an immuno-PCR assay for total PSA that has a limit of quantification >10 times lower than current ultrasensitive assays.
  
  
  METHODS
  The 2-site immunometric assay for total PSA employed 2 monoclonal antibodies, one conjugated to a double-stranded DNA label and the other bound to paramagnetic microparticles. After several washing steps, quantification cycles were determined and values were converted to PSA concentrations. We characterized analytical performance and compared accuracy with a commercially available total PSA assay.
  
  
  RESULTS
  The limit of quantification was 0.65 ng/L and the assay was linear in the range of 0.25-152.0 ng/L. Total imprecision estimates at PSA concentrations of 3.8, 24.1, and 69.1 ng/L were <15.2%, <9.4%, and <10.6%, respectively. Recovery of supplemented PSA ranged from 87.5% to 119.2% (mean 100.3%). Dilution recovery ranged from 96.4% to 115.3% (mean 102.3%). There was no high-dose hook effect up to 50 000 ng/L of PSA. Comparison with the commercial PSA assay showed a regression slope of 1.06 and a correlation coefficient of 0.996.
  
  
  CONCLUSIONS
  The analytical characteristics of the assay support the use of this assay for the accurate and precise measurement of serum PSA, even at sub-nanogram-per-liter concentrations.
authors.affiliation: Iris Molecular Diagnostics, Division of IRIS International, Inc., Carlsbad, CA, USA.
authors.forename: Jonathan E
authors.initials: JE
authors.lastname: McDermed
authors.forename: Ron
authors.initials: R
authors.lastname: Sanders
authors.forename: Stephen
authors.initials: S
authors.lastname: Fait
authors.forename: Robert E
authors.initials: RE
authors.lastname: Klem
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Sarno
authors.forename: Thomas H
authors.initials: TH
authors.lastname: Adams
authors.forename: Eleftherios P
authors.initials: EP
authors.lastname: Diamandis
mesh_terms: D000911:Antibodies, Monoclonal; D004247:DNA; D006801:Humans; D007118:Immunoassay; D057230:Limit of Detection; D008297:Male; D015345:Oligonucleotide Probes; D016133:Polymerase Chain Reaction / Q000379:methods; D011184:Postoperative Period; D017430:Prostate-Specific Antigen / Q000097:blood* / Q000235:genetics / Q000276:immunology; D011468:Prostatectomy; D011471:Prostatic Neoplasms / Q000097:blood / Q000601:surgery
chemical_list: D000911:Antibodies, Monoclonal; D015345:Oligonucleotide Probes; D004247:DNA; D017430:Prostate-Specific Antigen