PSA Standardization

Fixed Thresholds Produce Problems for Biopsy Recommendations

October 2009

A recent study in Clinical Chemistry reported the results of an ‘in-silico’ (or computer modeled) study where 106 samples were used to establish the bias between Hybritech and WHO calibrations.  Data from 5865 tests were then compared for biopsy recommendation and cancer detection.  In remarkable agreement with the analysis of the previous studies this study found a 19% decrease in the biopsy recommendation rate. These studies demonstrate the ~20% lower results from a WHO calibration result in missed opportunities for follow-up care for men who may be at risk for prostate cancer.  Clearly use of a fixed threshold can produce problems for further referrals for biopsy.

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• 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?