Biological Variation of Total Prostate-Specific Antigen: A Survey of Published Estimates and Consequences for Clinical Practice

Authors:
  • ASAxel Semjonow
    Axel Semjonow
  • PSPaul E.C. Sibley
    Paul E.C. Sibley
  • RLRolf Lamerz
    Rolf Lamerz
  • PPPer Hyltoft Petersen
    Per Hyltoft Petersen
  • WAWalter Albrecht
    Walter Albrecht
  • PBPeter Bialk
    Peter Bialk
  • MGMassimo Gion
    Massimo Gion
  • FJFrank Junker
    Frank Junker
  • HSHans-Peter Schmid
    Hans-Peter Schmid
  • HPHein Van Poppel
    Hein Van Poppel
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Abstract
Background: The objectives of this study were to determine whether a single result for total prostate-specific antigen (tPSA) can be used confidently to guide the need for prostate biopsy and by how much serial tPSA measurements must differ to be significant. tPSA measurements include both analytical and biological components of variation. The European Group on Tumor Markers conducted a literature survey to determine both the magnitude and impact of biological variation on single, the mean of replicate, and serial tPSA measurements. Methods: The survey yielded 27 studies addressing the topic, and estimates for the biological variation of tPSA could be derived from 12 of these studies. Results: The mean biological variation was 20% in the concentration range 0.1–20 μg/L for men over 50 years. The biological variation means that the one-sided 95% confidence interval (CI) of the dispersion for a single tPSA result is ∼33%. Three replicate samples with one analysis on each narrow the one-sided 95% CI for the mean concentration to ∼20% and facilitate decisions on prostate biopsy. During monitoring of serial measurements, the change needed for significance is ∼50% (P Conclusions: The biological variation of tPSA has implications for screening, diagnosis, and monitoring. Single measurements may not be sufficiently precise for screening and diagnosis. Replicate samples and calculation of the mean concentration may improve precision by reducing the dispersion. Monitoring of tPSA requires an estimate of either the change needed for significance or, alternatively, of the significance of the change.

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