Acid Phosphatase Reaction

In a variety of sexual offences, the seminal stain is usually encountered in a dried form on clothing worn by the participants of the offence as well as on other extraneous objects such as carpets, floor, grass, linoleum, mat; turf, wool, wood, and on the vaginal and rectal parts of the passive agent, depending upon the nature and circumstances of offence. The acid phosphatase reaction has now become an indispensable chemical test in the hands of a forensic scientist to identify the presence of semen which is an abundant source of the enzyme acid phosphatase (1). This enzyme acts optimally on monoesters of phosphoric acid at pH values around 5 to 6 (2). This test has been successfully employed to obtain a proof of the presence of seminal stains (3-12). The acid phosphatase reaction is a typical test in which the suspected seminal stain or an extract...

In a variety of sexual offences, the seminal stain is usually encountered in a dried form on clothing worn by the participants of the offence as well as on other extraneous objects such as carpets, floor, grass, linoleum, mat; turf, wool, wood, and on the vaginal and rectal parts of the passive agent, depending upon the nature and circumstances of offence. The acid phosphatase reaction has now become an indispensable chemical test in the hands of a forensic scientist to identify the presence of semen which is an abundant source of the enzyme acid phosphatase (1). This enzyme acts optimally on monoesters of phosphoric acid at pH values around 5 to 6 (2). This test has been successfully employed to obtain a proof of the presence of seminal stains (3-12). The acid phosphatase reaction is a typical test in which the suspected seminal stain or an extract of it on a filter paper is reacted with a solution of the substrate,

Abstract

OBJECTIVE:

To compare the effectiveness of the prostate specific antigen (PSA) test and the acid phosphatase (AP) test for semen detection in human vaginal samples.

MATERIAL AND METHOD:

The source materials were vaginal swabs that were tested at Ramathibodi Hospital between 2008 and 2010 from 2450 cases of raped women. Each swab was tested for semen by three methods: sperm detection by light microscopy, the AP enzymatic reaction, and the presence of PSA by using an immuno-chromatographic rapid kit test. The efficiencies of the AP and PSA tests were compared using the light microscopy result for the presence of sperm as the gold standard.

RESULT:

The specificities of the AP, the PSA and the combined AP-PSA tests were 96.4%, 92.3% and 91.9%, respectively, and the sensitivities were 65.5%, 80.4% and 84.5%, respectively. The receiver operating characteristic (ROC) area of the AP, PSA and combined AP-PSA tests were 0.8091,...