User:Hockeyetc08/Forensic serology

Saliva detection
Saliva is becoming a popular fluid diagnostic tool alternative to blood and urine. Some reasons are that it is an excellent noninvasive collection method, which even investigators with limited experience or training can complete without intrusion. Every individual's oral mucosa experiences shedding of its superficial layer of epithelial cells. This shedding can occur roughly every 2.7 hours, which means our saliva is found to contain ~75% exfoliated oral epithelial cells, ~25% leukocytes and microorganisms. Oral epithelial cells are also a convenient source of molecular DNA and allow easy access, collection, and regeneration potential. On average, 58% of epithelial cells collected from saliva samples are viable with complete genomic DNA.

Analysis of saliva has been slowly becoming famous for its many options of analysis. For example, when investigators analyze stain-type evidence on crime scenes, they may use a presumptive test to determine whether the stain is important to them or to confirm the possible type of bodily substance it may be. Compared to confirmatory tests, which are solid and sensitive and can identify specific biological components in the sample. A presumptive test to detect saliva is the alpha-amylase test, also known as the Phadebas Test.[4] This detection technique is based on the activity of the enzyme alpha-amylase, which breaks down starches from food into smaller oligosaccharide molecules, starting digestion in the mouth.[11] Using a petri dish gel, the saliva sample is added and allowed to diffuse through the gel overnight. Visualization is accomplished by adding iodine to the gel, which stains the starch in the gel blue. If saliva is present, then the alpha-amylase breaks down the starch, creating a clear-coloured circle around where the sample was placed. RSID tests have also been made in order to detect alpha-amylase, but they are not always reliable because there can be a lot of false positives.[3]

For confirmatory tests, there has not been as much research done compared to blood and semen. Since these tests specifically target amylase, confirmatory tests can not be done, considering amylase can be found in other bodily fluids.[12]