PSA Standardization

Analytical Differences¹⁵

October 2009

A study published in Clinical Chemistry in 2006 elegantly demonstrates that an increase of total PSA of 0.5 or 0.75 ng/mL/year, which are values used in the calculation of PSA velocity, can be the result simply of a change in the assay system used rather than an actual change in PSA concentrations.  Comparing five different immunoassays for total PSA produced variable results in that study, and all assays agreed within 15% of one another. However, some manufacturers, even though technically traceable to the WHO standard, produced patient results that mirrored the Hybritech assay results, which can be confusing and misleading.

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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?