Accessible Prostate-Specific Antigen Testing through Finger-Stick Dried Blood Spots and Routine Laboratory Analyzers

Prostate-specific antigen (PSA) is a biomarker used for detection, screening, and follow-up of prostate cancer. Traditional PSA quantification requires venipuncture, which poses challenges in collection, storage, and transportation. Dried blood spot (DBS) technology presents a promising alternative for measuring PSA levels, potentially facilitating telemedicine, and large-scale screening programs.

PSA concentrations were measured in paired capillary finger-stick DBS and venous serum samples from 75 patients using a Siemens immunochemistry analyzer. For DBS samples, PSA was extracted using PBS prior to analysis. Additional validation of stability, hematocrit effects, precision, and limits of blank and quantitation was performed according to corresponding Clinical and Laboratory Standards Institute standards.

The DBS PSA assay demonstrated good analytical performance, with total CVs of 4.5% and 6.1% at PSA concentrations of 11.5 µg/L and 3.8 µg/L, respectively. Limit of blank, limit of detection, and limit of quantitation were 0.24 µg/L, 0.28 µg/L, and 0.70 µg/L, respectively. Method comparison showed strong agreement between venous serum and finger-stick DBS (R2 = 0.987) with minimal bias. Stability studies showed that PSA remained stable for up to 31 days between -20°C and +30°C. Hematocrit affected measured PSA concentrations, but results remained within predefined total allowable error limits across 0.25-0.50 L/L. Variations in double spotting, blood volume, and number of spots did not affect PSA concentrations with a consistent trend.

PSA can be accurately measured from finger-stick DBS on an automated high-throughput immunochemistry analyzer. This method is less invasive for patients and may facilitate at-home self-sampling supporting (tele)diagnostics, screening, and follow-up.