Viability time of human saliva in the external environment for DNA Extraction and Purification: a scoping review

Abstract

The objective was to identify scientific evidence to answer the question: What is the viability time of human saliva for DNA extraction with human identification purposes? The search strategy was developed based on the focus question and adapted for each database (Pubmed, Web of Science, Scopus, LILACS, Cochrane Library and Google Scholar), with no restrictions for time of publication or language. Studies that explored only methodologies and materials related to DNA extraction were excluded, as well as articles that used DNA from components other than human saliva. There were identified 283 studies and, after the initial screening, 15 full-texts were assessed and analyzed, with only 6 studies being included due to confirmation of eligibility. Cigarette butts, dentures, dental compression tablets, oral cavity and FTA cards were the substrates analyzed for saliva analysis. The longest saliva viability time for human identification purposes reported was 11 years, with several protocols for DNA extraction being observed. As studies indicate that the sample collection and storage protocol is a factor that can influence the quantity and quality of the material examined it is suggested that further research be carried out due to the importance of the theme for the elucidation of legal cases.