Measurement of Prostate-specific Antigen by Use of a Novel Blood Collection and Analytical System

Background: Prostate-specific antigen (PSA) is widely used in the detection and monitoring of prostate cancer. We developed a system for the self-collection and transport of capillary whole blood for PSA analysis, with the goal of reducing phlebotomy visits and, thus, increasing the access and utilization of PSA in prostate cancer screening and monitoring.

Methods: The blood collection device [BIOSAFE Blood Transport System (BTSTM)] collects 70 μL of blood through a heparin-coated material into 200 μL of stabilizing solution. The diluted whole blood is used for measurement of PSA by a modified version of the Hybritech® Tandem-MP PSA Assay. Results were compared for matched samples of professionally and self-collected BTS blood and for matched BTS samples sera from blood collected by venipuncture. Imprecision for the whole-blood PSA measurement was estimated from analysis of whole-blood controls in duplicate, twice per day, over 20 days.

Results: BTS samples (n = 140) collected by a qualified healthcare professional compared with serum samples yielded the regression equation: y =1.02x + 0.04 (Sy|x = 0.35; r = 0.99). Comparison of the results for samples (n = 128) collected by the patient without professional assistance with serum samples yielded: y = 1.08x + 0.02 (Sy|x = 0.31; r = 0.99). The between-run CVs at 0.069, 0.53, 2.9, and 10.7 μg/L were 21%, 6.0%, 3.5%, and 3.8%, respectively. PSA was stable in BTS samples stored for 21 days at 18–24 °C and for 7 days at 37 °C.

Conclusion: The BIOSAFE BTS system allows accurate and convenient measurement of circulating PSA by a precise method for diluted whole blood.

Amperometric biosensors for detection of the prostate cancer marker (PSA)

Prostate specific antigen (PSA) has been identified as the most reliable clinical tool for diagnosing and monitoring prostate cancer (CAP). Since, there is no curative therapy available for prostate cancer, detecting the disease at the early stage is the best hope of increasing mortality rate. There are some procedures available for the detection of prostate cancer e.g. Tandem-R PSA, Hybritech Inc. (USA), IMx-PSA Abbott Laboratories (USA). However, these are time consuming and costly. We have developed a very simple and cost effective technique for identification and monitoring of prostate cancer using amperometric immunosensor. PSA is a glycoprotein with 93% peptide and 7% sugar content and isoelectric pH of 6.9. It may exist in the human serum as free (f-PSA) and complex (PSA-ACT) forms. Normally if the total PSA (t-PSA) level is more than 10 ng/ml, CAP is suspected. This paper presents an amperometric detection procedure for t-PSA using three electrode system in which working electrode (WE) is made of hydroxyethyl cellulose (HEC) and rhodinised carbon. The method used is rapid, very easy to use and involves low cost compared with other procedures. The electrochemical response was directly observed due to enzymatic reaction via a sandwich immunoassay on the WE. Monoclonal capture antibody (Mab) to PSA was immobilised on the WE and the other Mab labelled by the enzyme marker, horseradish peroxidase (HRP), was used as a tracer antibody.