Salivary Testing for SARS-CoV-2 Detection: Will It Help the Implant Dentist?

The entire dental profession has been in a state of confusion due to the recent increase in pandemic coronavirus disease 2019 (COVID-19) cases. The disease is caused by the SARS-CoV-2 virus. Dental team members are on the exposure-risk front line of this COVID-19 pandemic. It is well accepted that aerosolized saliva droplets of infected individuals are one of the main mechanisms for community transmission of the SARS-CoV-2 virus. Infected individuals maybe asymptomatic or symptomatic. This leads to the question: Which patients present a risk to dental care providers? This issue of risk has led to the recommendation that only necessary emergency dental care should be provided; however, a clear definition of the dental emergency is not agreed upon. Morbidity of dental disease left untreated becomes predictably worse, which makes a dental emergency more devastating and costly. This highlights the importance surrounding the issue of how dentists can know when it is “safe” to treat patients. This becomes even more important when invasive implant related procedures are necessary. These procedures may result in the patient's saliva becoming aerosolized. The American Dental Association has recommended taking a recent travel history and checking respiratory symptoms and body temperature as screening tools in conjunction with the dental team wearing a plethora of personal protective equipment (PPE).

Nasal or oropharyngeal COVID-19 testing methods are not easily accessible to everyone, nor do the results return quickly. It would be beneficial for the entire community if there were an accurate, quick, easy, and noninvasive diagnostic test for the detection of the SARS-CoV-2 virus. Currently, a nasopharyngeal swab (NPS) sample test (based on reverse transcription polymerase chain reaction [RT-PCR] laboratory test) is used to diagnosis COVID-19. The test results often take 1 to 14 days. In the interim, the patient is left in limbo. At the time of the test, if the patient were negative, they may become infected while waiting for the test results. Some studies suggest that oral fluids and saliva may be used for the detection of the SARS-CoV-2 virus. So, what is the evidence regarding the efficacy of saliva as a diagnostic specimen for COVID-19 patients?

Saliva has been reported to be positive for 2019-nCoV nucleic acid. The salivary glands, tongue, and lungs are considered possible hosts of 2019-nCoV due to expression of ACE2 receptors.¹  Additionally, ACE2 receptors are concentrated on the cell surfaces of epithelial cells of the tongue and oral mucosal tissues.²  ACE2 receptors are responsible for transporting the virus from the extracellular environment to intracellular sites, which leads to infection in the patient.

Hope within the community occurred on April 27, 2020 when the lay publication U.S. News and World Report reported on a Yale study that found saliva samples were more accurate and consistent than deep nasal swabs. They also reported that Yale University researchers and the NBA's National Basketball Players Association are in the process of conducting a study to evaluate the efficacy of a salivary test referred to as SalivaDirect. It is hypothesized to be a time- and cost-efficient method of determining if an individual is infected with the SARS-CoV-2 virus. Unfortunately, I was unable to locate the study in peer-reviewed literature.

Independent of the Yale group, Pasomsub et al.³  prospectively collected saliva samples and compared the reliability of salivary tests with the standard nasopharyngeal swab (NPS) and throat swab testing in persons seeking care at an acute respiratory clinic during a COVID-19 outbreak. RT-PCR tests were performed and the results of the two collection techniques compared.³  Two-hundred pairs of samples were collected and the agreement between the two specimens demonstrated a 97.5% observed agreement (κ coefficient 0.851, 95% CI 0.723–0.979; P < .001). They concluded: “Saliva might be an alternative specimen for the diagnosis of COVID-19. The collection is non-invasive, and non-aerosol generating. This method could facilitate the diagnosis of the disease, given the simplicity of specimen collection and good diagnostic performance.”³ 

Additionally, Rao et al.⁴  conducted a prospective study which recruited 217 isolated asymptomatic adult male participants in a COVID-19 quarantine center who had tested positive for SARS-CoV-2. Paired NPS and saliva specimens were collected and processed using real time RT-PCR that targeted envelope and RNA-dependent RNA polymerase genes. The results were compared. The Rao group concluded that saliva had a better detection rate of SARS-CoV-2 via RT-PCR assay in comparison to an NPS.⁴ 

However, Skolimowska et al.⁵  conducted a prospective cross-sectional study limited to acute symptomatic (<7-day duration) healthcare workers and their household contacts who presented to a COVID-19 specific clinic in London between April 28 and May 7, 2020. They concluded: “In our prospective UK cohort of mild community cases, comparing reverse transcription polymerase chain reaction … results from combined oropharyngeal/nasopharyngeal … swabs with saliva, we find saliva provides inferior sample adequacy with reduced sensitivity and negative predictive value ….”⁵ 

With salivary specimen self-collection being a noninvasive technique, SARS-CoV-2 surveillance could be easier and more accurate. Would it not be beneficial if patients could self-test prior to arriving at the dental clinic? If a patient was found to be negative, then implant eentists could perform complex, aggressive procedures with confidence and less concern about aerosolized saliva. Some of the cumbersome PPE could be replaced with conventional PPE. Salivary sampling would certainly be a cost-effective, easily accessible diagnostic tool and be of benefit to the entire community; however, further clinical studies are required before it becomes the standard of care.⁶