PSA Standardization

WHO 96/670 Total PSA Preparations¹⁶

October 2009

Interestingly, Dr. Klee at Mayo also evaluated the effect of matrix bias back in 2004 and showed that how or what the WHO standard is diluted with has an effect on the PSA results from different assays.  In that study, the WHO material was diluted into six different matrices, including PBS buffer with bovine serum albumin, 2 and 5% human serum albumin, manufacturer specific diluents and a synthetic matrix consisting of BSA, BGG (bovine gamma globulin), gelatin, and mannitol in PBS.

The graph on the left shows the total PSA standard at 4 ng/mL, and the graph on the right similar data but at 10 ng/mL.  Both graphs show the Access (which used the Hybritech calibrator) giving results that are higher than the Centaur (which used a WHO standard).  Variations in the standardization procedure for diluting the WHO standard, which is conducted by manufacturers, may account for some of the differences noted between assays that are traceable back to the same standard.

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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?