Francis DI, et al. Comparing saliva and blood for the detection of mosaic genomic abnormalities that cause syndromic intellectual disability. European Journal of Human Genetics. 2022; DOI: 10.1038/s41431-022-01232-5.

The study by Francis et al. (2022) selected patients who underwent CMA testing of both blood (n = 23,289) and saliva (n = 21,857) samples. The researchers aimed to determine whether SNP-microarray genomic testing of saliva had a greater diagnostic yield than blood for pathogenic copy number variants (CNVs).

Saliva samples were collected using the OC-175 (ORAcollect for pediatrics), a saliva collection kit. Results showed a statistically significant increase in the detection of tissue-limited mosaicism for pathogenic copy number changes in individuals with syndromic ID in samples taken from their saliva (9.1%) compared to their blood (0.44%). Conversely, there was no difference in the detection of non-mosaic copy number pathogenic changes between blood and saliva samples. This study proposes that in individuals with syndromic ID, saliva or buccal samples can be used for first-tier genomic testing instead of blood samples.

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Fitzsimons, E et al. Collection of genetic data at scale for a nationally representative population: the UK Millennium Cohort Study. Longitudinal and Life Course Studies, Volume 13, Number 1, January 2022, pp. 169-187(19)

The Millennium Cohort Study (MCS) is a diverse and representative birth cohort study of UK children born at the turn of the millennium. Data has been collected at seven time periods, spanning from infant to 17 years old with DNA samples from saliva collected at age 14. Due to the scale of the study, cost and logistic were important to consider, along with participant compliance rates over time.

Saliva samples, which are painless for the donor and relatively easily collected, are quickly becoming the preferred choice for a cost-effective, non-invasive source of high-quality genomic DNA for use in genetic analysis. Using the Oragene•DNA saliva collection kits and the UK postal system, the MCS created a DNA bank of over 23,000 samples from mothers, fathers and children or genetic trios. This data will be accessible for further research, joining the many biobanks looking to provide more robust and diverse genetic information.

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Hicks SD, et al. Diagnosing mild traumatic brain injury using saliva RNA compared to cognitive and balance testing. Clinical and Translational Medicine. 2020; 10:e197.

In a case-control study by Hicks et al. (2020), 251 participants with mild traumatic brain injury (mTBI) (≤14 days postinjury) were enrolled from 11 clinical sites. Saliva samples (n = 679) were collected at five time points (≤3, 4-7, 8-14, 15-30, and 31-60 days post-mTBI). Levels of various non-coding RNA (ncRNAs) (e.g., microRNA, small nucleolar RNA, and piwi-interacting RNA) were quantified within each sample using RNA sequencing.

Saliva samples were collected using highly absorbent ORAcollect swabs, which were applied under the tongue and near the parotid glands bilaterally for 10-15 s. This study demonstrates that saliva ncRNA levels may be used as an objective measure to identify mTBI status in concert with currently available clinical tools. In the present cohort, this biologic measure has similar diagnostic accuracy to neurocognitive or balance testing and displays additive value with standardized symptom assessment.

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Atkins, Rahshida, et al. "Eliciting Willingness and Beliefs towards Participation in Genetic Psychiatric Testing in Black/African American Mothers at Risk for Depression." Behavioral Sciences 10.12 (2020): 181.

It is well understood that the majority of historical genetic data is largely skewed towards European ancestry and there is a real need for diversity in genetic studies to promote health equity for underrepresented groups.

One study led by Dr. Atkins, investigated willingness to participate in genetic testing, specifically focused on Black/African American women at risk for depression. This study asked open-ended questions to solicit information on their beliefs, while providing information on saliva collection and DNA testing. As a result, 89.5% of the participants were willing to participate in salivary testing, though noted factors that could lower compliance rate including study knowledge, convenience of sample collection, or financial constraints. These conclusions indicate that saliva collection is an accepted form of genetic testing and study design must focus on reducing these barriers to ensure strong participation.

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Avgan N, et al. BDNF Variants May Modulate Long-Term Visual Memory Performance in a Healthy Cohort. International Journal of Molecular Sciences. 2017; 18(3):655.

Dr. Avgan’s group used saliva samples from Oragene•DNA^TM collection kits, to assess genetic variants in learning and memory studies. Using DNA extracted from saliva to investigate brain-derived neurotrophic factor (BDNF), they identified 10 variants nominally associated with immediate visual memory and 3 variants significantly associated with long-term visual memory. This led to their conclusion that BDNF has a potential role in the genetics of memory.

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