Molecular Form Differences Between Prostate-Specific Antigen (PSA) Standards Create Quantitative Discordances in PSA...

Area of Science:

• Biochemistry
• Oncology
• Clinical Diagnostics

Background:

• Prostate-specific antigen (PSA) assays for prostate cancer (PCa) detection suffer from low specificity, leading to high false positive rates.
• Current PSA assays struggle to differentiate between PCa and benign prostatic hyperplasia (BPH).
• PSA calibrants, derived from seminal plasma, contain a mixture of intact and cleaved molecular forms.

Purpose of the Study:

• To investigate if the molecular composition of PSA calibrants impacts the reliability of PSA testing.
• To determine the variability of intact and cleaved PSA forms in commercial PSA standards.

Main Methods:

• Western blot (WB) analysis of PSA standards from various commercial sources.
• Evaluation using multiple research-grade PSA ELISAs (Enzyme-Linked Immunosorbent Assays).

Main Results:

• All investigated PSA standards exhibited varying mass concentrations of intact and cleaved PSA molecular forms.
• Higher concentrations of intact PSA correlated with increased immunoassay absorbance values.
• Significant variability in PSA molecular composition was observed, even between different lots from the same manufacturer.

Conclusions:

• The heterogeneity of molecular forms in PSA calibrants contributes to the unreliability of PSA tests.
• Standardizing the mass concentration and purification of seminal plasma-derived PSA calibrants is crucial.
• Improved calibrant standardization will enhance the accuracy of PCa diagnostic measurements, including % free PSA and Prostate Health Index.