Comparison of the clinical validity of free prostate-specific antigen, alpha-1 antichymotrypsin-bound prostate-specific antigen and complexed prostate-specific antigen in prostate cancer diagnosis

Objective: To evaluate the diagnostic utility of free prostate specific antigen (fPSA), alpha-1-antichymotrypsin-bound PSA (PSA-ACT), complexed PSA (cPSA), and including their associated ratios to total PSA (tPSA) in serum for discrimination between prostate cancer (PCa) and benign prostatic hyperplasia (BPH). Methods: A total of 166 white men (age: 65-88 years) with a tPSA between 2 and 20 mug/l were retrospectively analysed. Serum concentrations of tPSA, fPSA, PSA-ACT and cPSA were measured in 118 untreated PCa patients and 48 patients with BPH. The tPSA and cPSA concentrations were measured with the Bayer Immune 1 system (Bayer Diagnostics, Tarrytown, USA). The Elecsys system 2010 (Roche Diagnostics, Mannheim, Germany) was used for determination of tPSA and fPSA. The PSA-ACT assay is a newly, developed prototype assay on the ES system (Roche Diagnostics, Mannheim, Germany). Results: For statistical analysis only patients with tPSA between 2 and 20 mug/l were enrolled. The median concentrations of tPSA (Bayer: PCa 7.36 mug/l, BPH 4.03 mug/l; Roche: PCa 7.75, BPH 4.13), PSA-ACT (PCa 6.98, BPH 3.18) and cPSA (PCa 6.46, BPH 3.20) were significantly different. The median ratios of fPSA/tPSA (PCa 12.8 vs. BPH 22.4%), PSA-ACT/tPSA (PCa 89.8 vs. BPH 76.1%) and cPSA/tPSA (PCa 90.5 vs. BPH 81.7%) were significantly different between PCa and BPH patients. Using the areas under the curves, receiver operating characteristics analysis (tPSA: 2-20 mug/l) for discrimination between PCa and BPH showed that the ratios fPSA/tPSA (area under the curve: 0.77), PSA-ACT/tPSA (0.72) and cPSA/tPSA (0.78) were significantly different from tPSA (Bayer: 0.53; Roche: 0.55). PSA-ACT (0.64) and cPSA (0.59) alone were not significantly different from tPSA. The calculated ratios fPSA/tPSA, PSA-ACT/tPSA and cPSA/tPSA were not significantly different. Conclusion: The determination of PSA-ACT or cPSA and the associated ratios do not improve the diagnostic impact to discriminate between PCa and BPH compared to fPSA/tPSA ratio. The ratios PSA-ACT/tPSA or cPSA/tPSA can be considered to be alternative tools of fPSA/tPSA. Copyright (C) 2001 S. Karger AG. Basel.