title: The biologic lower detection limit of six ultrasensitive PSA assays.
abstract: BACKGROUND
  The benefit of monitoring patients with prostate cancer (PCA) by ultrasensitive measurement of prostate specific antigen (PSA) is frequently discussed. Usually, the analytic lower detection limit of an ultrasensitive assay is determined by the manufacturer. As the analytic lower detection limit does not take into account interfering factors of human serum, the biologic lower detection limit, which is defined as PSA concentration detected in PSA-free human serum, plus 3 standard deviations, is of greater interest.
  
  
  METHODS
  We investigated the biologic lower detection limit of six ultrasensitive PSA assays. Sera from 15 men with bladder cancer after radical cystoprostatectomy and from 30 healthy women were applied. Hence, we expected no PSA of prostatic origin.
  
  
  RESULTS
  The biologic lower detection limit obtained using these sera was up to 30 fold higher (men, 0.29-0.63 ng/ml; women, 0.03-0.69 ng/ml) than the analytic lower detection limit (0.01-0.09 ng/ml).
  
  
  CONCLUSIONS
  PSA measurement in sera obtained from men without prostate and women results in PSA values above the ultrasensitive range. Therefore, advantages provided by ultrasensitive PSA measurement in monitoring PCA patients after radical prostatectomy are limited.
authors.affiliation: Institut für Klinische Chemie und Laboratoriumsmedizin, Westfälische Wilhelms-Universität Münster, Germany. junkerr@uni-muenster.de
authors.forename: R
authors.initials: R
authors.lastname: Junker
authors.forename: B
authors.initials: B
authors.lastname: Brandt
authors.forename: A
authors.initials: A
authors.lastname: Semjonow
authors.forename: M
authors.initials: M
authors.lastname: Erren
authors.forename: C
authors.initials: C
authors.lastname: Zechel
authors.forename: G
authors.initials: G
authors.lastname: Assmann
mesh_terms: D004784:Environmental Monitoring; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009362:Neoplasm Metastasis; D017430:Prostate-Specific Antigen / Q000097:blood*; D011471:Prostatic Neoplasms / Q000097:blood* / Q000175:diagnosis / Q000601:surgery; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012727:Sex Characteristics
chemical_list: D017430:Prostate-Specific Antigen