Determination of Free-PSA (fPSA) and fPSA/PSA-Ratio Using A Point-of-Care Device

Prostate specific antigen (PSA) and free PSA (fPSA) are important tools for diagnosing prostate cancer (PC). Efforts are continuously undertaken to provide more patient-centered healthcare. The application of point-of-care (POC) systems for laboratory analyses represents a step in this direction. Previous investigations on total PSA measurements using a POC system (concile® Ω100 POC reader) showed good concordance with standard laboratory measurements. For the same POC reader a novel system for fPSA was developed. In the current study, we prospectively evaluated the quality of the POC system for fPSA.

Sixty-four patients undergoing PSA measurements in our outpatient clinic between 06/2015 and 09/2015 were enrolled in the study. We measured total PSA (tPSA) and fPSA with a POC reader system (concile® Ω100) and a standard laboratory system (Siemens Immulite 2000®) and compared the respective results using linear regression analyses for PSA, fPSA, and fPSA/tPSA ratio (%fPSA).

The coefficients of determination (r²) for fPSA and %fPSA were 0.85 (p < 0.001) and 0.82 (p < 0.001) in the subgroup with total PSA between 4 and 10 ng/mL. In the subgroup with tPSA ≤ 4 ng/mL, r² for fPSA concile® was 0.55 (p < 0.001) and 0.10 (p = 0.088) for %fPSA. In the subgroup of tPSA > 10 ng/mL the r² for fPSA and %fPSA was 0.50 (p = 0.022) and 0.50 (p = 0.022), respectively.

The POC fPSA values correlated well with the laboratory analyses, specifically in the clinically relevant diagnostic range of tPSA 4 - 10 ng/mL. These results complement the tPSA data obtained previously and indicate the reliability of the fPSA method and the resulting %fPSA score.