The evaluation and validation of Phadebas® paper as a presumptive screening tool for saliva on forensic exhibits

Abstract

The Phadebas Forensic Press Test is routinely used for the detection of saliva. However, assessment of the use of Phadebas paper for this purpose has not been studied extensively. The suitability of Phadebas paper as a presumptive screening tool for saliva on forensic exhibits, was investigated by analysing the following: (1) sensitivity, (2) specificity, (3) effects of temperature on sensitivity and specificity, (4) detection of saliva in mixed body fluid samples, and (5) influence of substrate porosity. The results of this study demonstrated that Phadebas paper is more sensitive to α-amylase activity and less specific for saliva than previously reported. The use of an examination temperature of 37°C had no effect on sensitivity, but increased the incidence of cross-reactivity with other forensically relevant body fluid stains. Blood, urine and vaginal secretions can inhibit the detection of α-amylase activity with Phadebas paper in mixed stains of saliva and body fluid. Substrate porosity is a weak predictor for the time taken for a saliva stain to achieve a strong positive result on Phadebas paper. Overall, this study demonstrated that the Phadebas Forensic Press Test has limitations as a presumptive test for the accurate identification of saliva.

A Proposed Procedure for Discriminating between Nasal Secretion and Saliva by RT-qPCR

“…However, such specific genes have not been reported for nasal secretion to date. Saliva is also difficult to identify precisely, because various markers for saliva are detected in other body fluids such as nasal secretion [ 4 , 5 , 6 , 7 , 27 , 28 ].…”

“…However, such specific genes have not been reported for nasal secretion to date. Saliva is also difficult to identify precisely, because various markers for saliva are detected in other body fluids such as nasal secretion [4][5][6][7]27,28]. Accordingly, in this study, we attempted to develop a specific procedure for discriminating between nasal secretion and saliva for forensic purposes.…”

“…Further, saliva is one of the main body fluids left at crime scenes, and analysis results can prove useful in various criminal cases, especially sexual assaults. However, presumptive and confirmatory tests for saliva based on α-amylase activity or protein [ 1 , 2 , 3 ] can show cross-reactivity with other body fluids [ 4 , 5 , 6 , 7 ], such as nasal secretion. Therefore, a procedure for discriminating between nasal secretion and saliva could be valuable in criminal casework.…”

Current methods for stress marker detection in saliva

“… Amperometry [ 131 ] n.s. 1.1 U/mL SPCE, indirect determination, POC Colorimetric Assay [ 135 ] [ 136 ] n.s. n.s.…”

Biomarker assay systems for onsite monitoring of fatigue

“…Currеnt dеvеlopmеnts in thе еlaboration of еnzymatic assays for thе α-amylasе dеtеction includе еlеctrochеmical (potеntiomеtry [61,62], ampеromеtry [63,64], cyclic voltammetry [65]), piezoelectric methods [66] and immunoassays [67]. The ability of amylase to cleave α-bonds of polysaccharides was widely utilized for elaboration of colorimetric detection methods [68][69][70][71][72][73][74][75][76][77]. A summary of methods can be found in table 2.4.1.…”