Testing for COVID-19 in dental offices: Mechanism of action, application, and interpretation of laboratory and point-of-care screening tests

Abstract

Background: The dental office potentially possesses all transmission risk factors for severe acute respiratory syndrome coronavirus 2. Anticipating the future widespread use of COVID-19 testing in dental offices, the authors wrote this article as a proactive effort to provide dental health care providers with current and necessary information surrounding the topic.

Methods: The authors consulted all relevant and current guidelines from the Centers for Disease Control and Prevention and the US Food and Drug Administration, as well as online resources and review articles.

Results: Routine COVID-19 screening and triage protocols are unable to detect all infected people. With the advancements in diagnostic tools and techniques, COVID-19 testing at home or in the dental office may provide dentists with the ability to evaluate the disease status of their patients. At-home or point-of-care (POC) tests, providing results within minutes of being administered, would allow for appropriate measures and rapid decisions about dental patients' care process. In this review, the authors provide information about available laboratory and POC COVID-19 screening methods and identify and elaborate on the options available for use by dentists as well as the regulatory requirements of test administration.

Conclusions: Dentists need to be familiar with COVID-19 POC testing options. In addition to contributing to public health, such tests may deliver rapid, accurate, and actionable results to clinical and infection control teams to enhance the safe patient flow in dental practices.

Practical implications: Oral health care must continue to offer safety in this or any future pandemics. Testing for severe acute respiratory syndrome coronavirus 2 at the POC offers a control mechanism contributing to and enhancing the real and perceived safety of care in the dental office setting.

Keywords: COVID-19 testing; SARS-CoV-2; aerosols; antibody; antigen; dentistry; oral fluids; point-of-care testing; saliva; surveillance.

Copyright © 2021 American Dental Association. Published by Elsevier Inc. All rights reserved.

Figures

Figure 1

Fundamentals of COVID-19 testing. A. COVID-19 biomolecules can be detected in oral fluids as well as other sites and specimens. A detailed description and comprehensive review of these specimens' characteristics and viral loads and detection rates of COVID-19 is provided by Shirazi and colleagues.B. Schematic representation of detection window for COVID-19 biomarkers. The best detection and testing time for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA and antigen is up to 14 days from symptom onset. Immunoglobulin M (IgM) antibody against SARS-CoV-2 is detectable days after symptom onset, peaks during week 2, and will start to disappear at approximately week 4. Immunoglobulin G (IgG) against SARS-CoV-2 antibody will be detectable at approximately week 2 and persist for an unknown time. The duration of persistence of IgG antibody is not fully clear yet. C. COVID-19 biomarkers are detected with various laboratory methods that have different mechanism of action. Figure 2, Figure 3, Figure 4 include detailed description of each method. POC: Point-of-care.

Figure 2

Mechanism of action of nucleic acid amplification tests (NAATs). NAATs generally require 5 steps, which are modified or merged in different NAATs. The 5 steps are lysis of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) viral particles in the sample; purification of the viral RNA; reverse transcription of the RNA to complementary DNA (cDNA), which produces DNA templates for the next step; thermocyclic or isothermal amplification of specific regions (target genes) of the cDNA using gene-specific primers, DNA polymerases, and probes to amplify only the selected region; and detection of the amplified cDNA, which can happen during or after step 4. The difference among various NAATs arise from modification of these steps. Some NAATs do not require separate lysis and purification steps, whereas some others merge reverse transcription and amplification. Analytical accuracy of COVID-19 NAATs depends mainly on the primer or probe design, and different assays use different primer or probe sets targeting different regions of the SARS-CoV-2 genome. Some NAATs, including isothermal methods, are authorized for point-of-care COVID-19 diagnostics and provide fast, sensitive, high-efficiency, and cost-effective results without need for specialized equipment.

Figure 3

Mechanism of action of antigen tests. Point-of-care antigen tests typically are lateral flow assays and come with a test strip or cassette composed of multiple overlapping pads. The clinical sample needs to be placed in a tube containing the extraction reagent after collection, which disrupts the viral particle and exposes the viral proteins. Next, the sample is added to the sample pad, where it starts to travel via capillary action through the conjugate pad and conjugates with the fluorescence-labeled severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) detection antibody or the detector-antibody gold conjugate. Next, it flows through an analytical membrane striped with a capture antibody specified as the test line. Most tests include a control line after the test line to validate proper fluid flow and the activity of assay reagents. The final outcome might be read via an instrument or displayed as colored lines for naked-eye reading.

Figure 4

Mechanism of action of antibody tests. The authorized point-of-care serologic tests commonly are based on lateral flow immunoassay, which detect binding antibodies. Lateral-flow immunoassays are composed of a cassette that encloses strip membranes. After the specimen is added to the sample pad, it moves forward by capillary action through the conjugated pad, where the present immunoglobulin G (IgG) and immunoglobulin M (IgM) antibodies in the sample interact with impeded gold conjugated severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antigens and rabbit-gold conjugated antibodies. The created antigen-antibody complexes move forward to the analytical membrane and bind antihuman IgG and IgM antibodies (capture antibodies) at the test line and get immobilized, whereas the rabbit-gold conjugate antibodies bind to antirabbit IgG antibodies at the control line and get immobilized. The result will be visible as colored lines owing to the accumulation of gold particles. Depending on whether the test is for IgM- or IgG-class antibodies or both, the test may show 1, 2, or 3 stripes.

eFigure

Antigen testing algorithm based on CDC recommendation. 1No known exposure to a person with COVID-19 within the past 14 days. 2Single, multiple, or continuous known exposure to a person with COVID-19 within the past 14 days; perform NAAT first if short turnaround time is available, if the person cannot be effectively and safely quarantined, or if there are barriers to possible confirmatory testing. 3If prevalence of infection is not low in the community, clinical discretion should consider whether this negative antigen result requires confirmation. 4If a symptomatic person has a low likelihood of SARS-CoV-2 infection, clinical discretion should determine if this negative antigen test result requires confirmatory testing. 5In instances of higher pretest probability, such as high incidence of infection in the community, clinical discretion should determine if this positive antigen result requires confirmation. 6In certain settings, serial antigen testing could be considered for those with a negative antigen test result; serial testing may not require confirmation of negative results. The role of a negative antigen test result in ending quarantine depends on when it is performed in the quarantine period. See CDC’s Options to Reduce Quarantine for guidance on use of antigen testing for this purpose and when a negative antigen test result indicates no infection with SARS-CoV-2. 7Nucleic acid amplification test; confirm within 48 hours using an NAAT, such as reverse transcription polymerase chain reaction, that has been evaluated against the Food and Drug Administration’s reference panel for analytical sensitivity. 8Known exposure to a person with COVID-19 within the past 14 days; if unsure, clinical discretion should determine whether isolation is necessary. 9Isolation is necessary. 10Quarantine is necessary. Clinical discretion should determine if and when additional testing is necessary.