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One-step immunostrip test for the simultaneous detection of free and total prostate specific antigen in serum

Lookup NU author(s): Dr Cesar Fernandez-Sanchez, Emeritus Professor Calum McNeilORCiD, Professor Hing Leung, Vincent Gnanapragasam


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The development of a one-step lateral flow immunoassay on a strip format for the rapid and reliable simultaneous detection of serum levels of free and total prostate specific antigen (f-PSA and t-PSA) and estimation of f-PSA to t-PSA ratio (f/t-PSA) is reported. The f/t-PSA ratio has shown to be more specific for the correct diagnosis of prostate cancer than t-PSA alone, especially in the so-called diagnostic grey zone of 4-10 μg/l t-PSA. The performance of the system described relied on non-competitive immunoassay protocols. Herein, f-PSA and t-PSA were sandwiched between anti-f-PSA and anti-t-PSA monoclonal antibodies immobilised on the strip and a colloidal gold anti-PSA antibody tracer. In the presence of PSA in the sample, the tracer accumulated on the strip results in the appearance of specific pink colour lines. The colour intensity of these lines was found to be directly proportional to the PSA concentration and a semi-quantitative estimation could be carried out visually. Quantitative analysis was also possible by densitometry. Using PSA standards prepared in female serum, the strip could be calibrated up to a concentration of 60 μg/l for both PSA species, with an assay time of less than 20 min. The estimated detection limit was 1 μg/l in all cases. The immunostrip showed good storage stability for at least 2 months and the reproducibility was always between 12% and 17%. Fifty-one male serum samples were analysed with the strip and results compared with values obtained by two different commercial immunoassays taken as reference methods. The study yielded acceptable correlation and agreement. An estimation of the sensitivity and specificity demonstrated the strip validity as a potential front-line device for the early detection of prostate cancer and differentiation of benign prostatic anomalies. Small plastic cartridges incorporating the immunostrip and a small blister containing washing solution that helps remove unbound species from the strip were envisaged in order to avoid false positive readings and decrease background signals, thereby leading to better sensitivity and detection limits. © 2005 Elsevier B.V. All rights reserved.

Publication metadata

Author(s): Fernandez-Sanchez C, McNeil CJ, Rawson K, Nilsson O, Leung HY, Gnanapragasam V

Publication type: Article

Publication status: Published

Journal: Journal of Immunological Methods

Year: 2005

Volume: 307

Issue: 1-2

Pages: 1-12

ISSN (print): 0022-1759

ISSN (electronic): 1872-7905

Publisher: Elsevier BV


DOI: 10.1016/j.jim.2005.08.014

PubMed id: 16277989


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