PSA Standardization

Development of PSA Standards

October 2009

Perhaps it may help to examine the evolution of PSA testing even further.  The first PSA assay was a dual monoclonal radioimmunoassay manufactured by Hybritech and referred to as Tandem-R assays.  The concentration of the purified PSA used to standardize the Hybritech assay back in 1984 was determined based on Lowry protein methods, which were what was available at that time.  In 1991, the Hybritech assay became an automated immunoassay on the Beckman Access and first used in prostate cancer screening after further FDA approval in 1994. Efforts to standardize PSA assays were initiated in 1992 by Dr. Thomas Stamey at the First Stanford Conference. At the Second Stanford Conference on International Standardization of Prostate-Specific Antigen in 1994, Dr. Stamey and colleagues proposed use of a primary calibrator consisting of 90% purified PSA-complexed to alpha1-antichymotrypsin and 10% free PSA (later termed the 90:10 standard) on a molar basis.

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Jump to section:

• Introduction
• Elevated PSA Result on Screening
• Reasons for Ordering PSA¹
• PSA Screening in the News
• Recommendations for Screening
• Arguments for Screening for Prostate Cancer
• Recommendations for Not Screening
• Arguments Against Screening for Prostate Cancer
• PSA Sensitivity and Specificity
• High-Grade Prostate Cancer is Not Rare When PSA =4.0 ng/mL⁶
• Increase Specificity Using PSA Velocity⁸
• Optimizing Clinical Sensitivity and Specificity: Age/Ethnic Reference Intervals^9,10
• Utilization of Free/Total PSA Ratio¹¹
• Why Aren't PSA Results Interchangeable?
• Development of PSA Standards
• Development of PSA Standards
• Effect of Analytical Bias on Classification Based on Fixed Criteria
• Analytical Difference: Results per 1000 Patients Tested¹³
• Hybritech vs. WHO Standardized Assays^12,14
• Analytical Differences¹⁵
• CAP Proficiency Testing
• WHO 96/670 Total PSA Preparations¹⁶
• WHO Calibration/Concordance at 3.1 ng/mL Cutoff⁵
• WHO Calibration/Concordance at 3.1 ng/mL Cutoff⁵
• WHO Calibration/Concordance at 4.0 ng/mL Cutoff⁵
• Clinical Differences in PSA Screening¹⁴
• The Clinical Difference
• Fixed Thresholds Produce Problems for Biopsy Recommendations
• Effect on "Watchful Waiting"
• Effect on "Watchful Waiting"
• Adding Biological Variability into the Mix
• Futures in Prostate Cancer Testing?
• PSA Testing at Mayo
• Conclusions
• References
• References
• Questions?