Saliva has become an increasingly important biological fluid for non-invasive diagnostic and research purposes. With advancements in genetic testing and microbiome analysis, saliva is now a valuable starting material for a range of applications, from genetic testing to monitoring the oral microbiome.
Human saliva contains a wide array of biomarkers, including DNA, RNA, proteins, hormones, and metabolites, making it an ideal candidate for diagnostic testing (1). As a non-invasive specimen, saliva collection is easy, safe, and comfortable for patients, providing a significant advantage over other sample types like blood. Among the various applications of saliva, two key areas stand out: genetic testing and oral microbiome analysis.
Saliva has proven to be a reliable source for genetic testing, as it contains genomic DNA that can be extracted with high yield and quality. Genomic DNA is found in buccal cells, saliva gland cells, and epithelial cells present in the oral cavity, making it a suitable medium for both individual genetic tests (e.g., ancestry, genetic disorders) and large-scale population studies.
Saliva-based genetic testing has been gaining popularity due to its convenience and accuracy. Studies have shown that DNA extracted from saliva samples is comparable to DNA from other sources such as blood, offering similar reliability for genotyping and sequencing applications (2). Technologies like PCR (Polymerase Chain Reaction) and NGS (Next-Generation Sequencing) are routinely employed for analyzing the DNA obtained from saliva, allowing for high-throughput genetic diagnostics and personalized medicine.
Another prominent use of saliva is for oral microbiome testing. The oral cavity hosts a diverse microbial community, including bacteria, viruses, fungi, and archaea, which play crucial roles in oral health and disease.
Recent research has underscored the significant link between oral microbiota and systemic diseases (3). Dysbiosis in the oral cavity has been associated with a range of systemic conditions, including cardiovascular diseases, aspiration pneumonia, Alzheimer disease (see figure 1). For instance, studies have shown that P. gingivalis, a bacterium causing periodontal disease, causes neuronal inflammation, degrades tau protein causing neurofibrillary tangles and contributes to the formation of amyloid-β plaques (4).
Figure 1: The figure shows several diseases linked to oral microbiota. Each inset highlights the underlaying mechanism. Figure from Baker et al. 2024.
Analyzing the microbial composition of saliva can significantly enhance both preventive and therapeutic strategies in dentistry and general health care.
While saliva offers numerous advantages as a diagnostic tool, the reliability of results depends on the quality of the sample collected. DNA-based molecular methods, like PCR, NGS, and 16S rRNA gene sequencing, commonly employed for genetic testing and microbiome analysis, necessitate an adequate quantity of high-quality, pure, and intact DNA. Saliva, being a complex biological fluid, contains components that can degrade DNA and RNA over time, leading to unreliable test results if not properly preserved. Therefore, the stabilization of saliva samples is a critical step in ensuring the accuracy of downstream analysis.
To facilitate the reliable collection and stabilization of saliva samples, several commercial products have been developed. These advancements have significantly improved the reliability and convenience of saliva-based diagnostics, making it a preferred method for various applications, including genetic testing and microbiome analysis.
The SalivaGene Swab Comfort (CE-IVD) is a swab-based system designed for easy and reliable collection of buccal cells and saliva, including a stabilization solution to preserve nucleic acids at the time of collection for 6 months at room temperature. The SalivaGene Collector (CE-IVD) offers an alternative collection method, allowing for whole saliva collection while ensuring the preservation of both human and microbial DNA through the inclusion of a lyophilized stabilization buffer for 12 months at room temperature. Both systems are designed for self-collection, enabling broad accessibility without the need for specialized personnel, making it ideal for large-scale genetic and microbiome studies.
Once a saliva sample has been collected using one of the aforementioned devices, the PSP SalivaGene DNA Kit (CE-IVD) offers the perfect solution to extract high-quality DNA for subsequent analysis. The kit is optimized for extracting DNA from saliva samples preserved with the SalivaGene Swab Comfort or SalivaGene Collector, ensuring high yields and purity.
Deeley et al. evaluated five commercially available saliva collection kits for DNA extraction and demonstrated that the SalivaGene collection and DNA extraction exhibited superior performance in DNA yield and purity (5). The study reported DNA yields exceeding 30 µg per sample, along with high-quality DNA suitable for downstream applications such as PCR and NGS.
Professionals worldwide have great confidence in the performance of the SalivaGene products and are using them for a wide range of applications, including genetic testing and microbiome analysis (6, 7, 8, 9). Reliability and effectiveness of these product have made them a preferred choice in both clinical and research settings.
Saliva has emerged as a powerful and non-invasive tool for genetic and microbiome testing, enabling researchers and clinicians to gain valuable insights into oral health and genetic predispositions. As with any biological sample, the quality and reliability of test results depend on proper collection, stabilization, and extraction methods. Advances in stabilization technologies, such as the SalivaGene products, ensure that saliva samples can be preserved for accurate and consistent analysis. By leveraging these innovations, saliva can be reliably used for a wide range of diagnostic and research applications, offering a promising future for personalized medicine and oral health monitoring.
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