Editing Prostate-specific antigen (section)

==Forensic identification of semen==

PSA was first identified by researchers attempting to find a substance in seminal fluid that would aid in the investigation of rape cases.<ref>{{Cite journal |vauthors=Hara M, Inorre T, Fukuyama T |title=Some physicochemical characteristics of gamma-seminoprotein, an antigenic component specific for human seminal plasma |journal= Jpn J Legal Med |year=1971 |volume=25 |pages=322–324}}</ref> PSA is used to indicate the presence of [[semen]] in forensic [[serology]].<ref>{{cite journal | vauthors = Gartside BO, Brewer KJ, Strong CL | title = Estimation of Prostate-Specific Antigen (PSA) Extraction Efficiency from Forensic Samples Using the Serateca PSA Semiquant Semiquantitative Membrane Test | journal = Forensic Science Communications | volume = 5 | issue = 2 | date = April 2003| url =https://www.fbi.gov/hq/lab/fsc/backissu/april2003/gartside.htm | access-date = 2008-05-11 |archive-url = https://web.archive.org/web/20080409190231/http://www.fbi.gov/hq/lab/fsc/backissu/april2003/gartside.htm <!-- Bot retrieved archive --> |archive-date = 2008-04-09 |url-status = live }}</ref> The semen of adult males has PSA levels far in excess of those found in other tissues; therefore, a high level of PSA found in a sample is an indicator that semen may be present. Because PSA is a [[biomarker]] that is expressed independently of [[Spermatozoon|spermatozoa]], it remains useful in identifying semen from [[vasectomy|vasectomized]] and [[azoospermia|azoospermic]] males.<ref name="Hochmeister-1999">{{cite journal | vauthors = Hochmeister MN, Budowle B, Rudin O, Gehrig C, Borer U, Thali M, Dirnhofer R | title = Evaluation of prostate-specific antigen (PSA) membrane test assays for the forensic identification of seminal fluid | journal = Journal of Forensic Sciences | volume = 44 | issue = 5 | pages = 1057–1060 | date = September 1999 | pmid = 10486959 | doi = 10.1520/JFS12042J }}</ref>

PSA can also be found at low levels in other body fluids, such as urine and breast milk, thus setting a high minimum threshold of interpretation to rule out [[Type I and type II errors|false positive]] results and conclusively state that semen is present.<ref name="Laux-2005"/> While traditional tests such as crossover [[electrophoresis]] have a sufficiently low sensitivity to detect only seminal PSA, newer diagnostics tests developed from clinical [[prostate cancer screening]] methods have lowered the threshold of detection down to 4{{nbsp}}ng/mL.<ref>{{cite journal | vauthors = Hochmeister MN, Budowle B, Rudin O, Gehrig C, Borer U, Thali M, Dirnhofer R | title = Evaluation of prostate-specific antigen (PSA) membrane test assays for the forensic identification of seminal fluid | journal = Journal of Forensic Sciences | volume = 44 | issue = 5 | pages = 1057–1060 | date = September 1999 | pmid = 10486959 | doi = 10.1520/JFS12042J | url = http://journalsip.astm.org/jofs/PAGES/3097.htm | url-status = dead | archive-url = https://web.archive.org/web/20041024194221/http://journalsip.astm.org/jofs/PAGES/3097.htm | archive-date = 2004-10-24 | url-access = subscription }}</ref> This level of antigen has been shown to be present in the peripheral blood of males with prostate cancer, and rarely in female urine samples and breast milk.<ref name="Laux-2005"/>