Production, analysis, and characterization of reference materials for prostate-specific antigen

Area of Science:

• Biochemistry
• Clinical Chemistry
• Oncology

Background:

• Prostate cancer screening relies on accurate measurement of prostate-specific antigen (PSA).
• Existing reference materials may not accurately reflect the molecular forms of PSA found in patient serum.
• Variability in PSA assay results across different clinical laboratories necessitates the development of improved standardization tools.

Purpose of the Study:

• To develop and validate reference materials for PSA assays, mimicking patient sera across clinically relevant concentration ranges (0.5-10.0 ng/mL).
• To evaluate the performance of commercial PSA assays using these novel reference materials.
• To characterize the molecular forms of PSA in the reference materials and compare them to clinical specimens.

Main Methods:

• Pooled serum from healthy individuals and patients with elevated PSA was lyophilized to create reference materials.
• These materials, along with semen-supplemented proficiency testing samples, were distributed to clinical laboratories.
• Gel filtration chromatography (Sephacryl S-200-HR) was used to analyze the molecular forms of PSA.

Main Results:

• Commercial PSA assays showed good agreement (within +/- 12%) when measuring PSA in the developed reference materials.
• Significant discrepancies (up to 1.8-fold) were observed when assays were tested with semen-supplemented samples, highlighting matrix effects.
• Reference materials were predominantly alpha 1-antichymotrypsin-bound PSA (~90%), similar to clinical specimens, unlike semen-supplemented samples (~40%).

Conclusions:

• Semen-free reference materials containing endogenous PSA closely mimic clinical specimens.
• These materials are valuable for standardizing clinical PSA assays and improving the accuracy of prostate cancer screening.
• Understanding PSA molecular forms is crucial for inter-assay consistency.