Interassay Variability and Clinical Implications of Five Different Prostate-specific Antigen Assays

Area of Science:

• Urology
• Clinical Chemistry
• Oncology

Background:

• Prostate-specific antigen (PSA) is essential for prostate cancer (PCa) detection and monitoring.
• Historical variability in PSA assays necessitates reassessment with current technologies.
• Latest generation PSA assays require evaluation for interassay variability.

Purpose of the Study:

• To evaluate interassay variability of the latest generation of five commercial PSA assays.
• To compare total PSA (tPSA) and free-to-total PSA ratio (%fPSA) across assays.
• To analyze the impact of assay variability on PCa diagnosis.

Main Methods:

• Tested five commercial PSA assays on blood samples from 76 men prior to prostate biopsy.
• Compared tPSA and %fPSA values, using Roche as the benchmark.
• Employed Passing-Bablok regression and Bland-Altman plots for statistical analysis.

Main Results:

• Substantial variability in tPSA and %fPSA values observed across the five assays.
• tPSA values ranged from 20.7% lower to 9.6% higher compared to the Roche assay.
• %fPSA values varied by up to 15.7% between assays.
• Assay variability could lead to at least 14% discrepancy in diagnostic sensitivity and specificity.

Conclusions:

• Significant interassay variability exists even with the latest PSA assays.
• Standardized calibration methods are urgently needed.
• Clinicians must be aware of assay-specific thresholds for accurate PCa diagnosis and monitoring.