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A universal calibrator for prostate specific antigen (PSA)
A F Prestigiacomo1, Z Chen, T A Stamey
1Department of Urology, Medical Center, Stanford University, California, USA.
Summary
This study details a reproducible method for purifying the prostate-specific antigen (PSA) and alpha-1-antichymotrypsin (ACT) complex. A novel calibrator is proposed for standardizing PSA immunoassays globally.
Area of Science:
- Biochemistry
- Analytical Chemistry
Background:
- Prostate-specific antigen (PSA) and alpha-1-antichymotrypsin (ACT) form a complex in vivo.
- Accurate quantification of the PSA-ACT complex is crucial for clinical diagnostics.
Purpose of the Study:
- To establish a robust protocol for purifying the in vitro generated PSA-ACT complex.
- To characterize the purified PSA-ACT complex and develop a universal calibrator for PSA immunoassays.
Main Methods:
- Purification using sequential gel filtration and ion-exchange chromatography.
- Purity confirmation via gel electrophoresis and Western blot.
- Characterization including amino acid analysis for extinction coefficient and molecular weight determination.
Main Results:
- Achieved apparent homogeneity of the PSA-ACT complex with high reproducibility.
- Assigned an extinction coefficient of 1.0 x 280 nm (L x g-1 x cm-1) and a molecular weight of 89,280 Da.
- Developed two calibrators: 100% PSA-ACT and a 90:10 PSA-ACT/free PSA mixture.
Conclusions:
- The developed purification protocol is effective and reproducible.
- The 90:10 PSA-ACT/free PSA calibrator is recommended for international standardization of PSA immunoassays.