Research Roundup: Nucleic Acid Specimen Transport and eNat®
November 13, 2021
Welcome to Research Roundup! Each month COPAN will feature a comprehensive review and commentary on recent scientific publications covering a particular topic of interest. COPAN’s Research Roundup is authored by Dr. Susan Sharp, COPAN’s Scientific Director!
In this month’s edition, Dr. Sharp reviews nucleic acid specimen transport and COPAN’s eNat®, a FDA cleared sample collection system intended to safely inactivate and stabilize samples containing microorganisms such as SARS-CoV-2, preparing the samples for reliable downstream molecular testing.
About Dr. Susan Sharp
Dr. Sharp has been a clinical microbiologist and a very active member of The American Society for Microbiology (ASM) for 30 years serving on various boards and committees. She is a Diplomat of the American Board of Medical Microbiology (ABMM) and a Fellow in the American Academy of Microbiology. Dr. Sharp served as the Chair of the ASM Public and Scientific Affairs Board’s Committee on Laboratory Practices from 2007 to 2015, as well as Chair of the Examination Development committee and Vice-Chair of the ABMM during 1999-2015.
Dr. Sharp has recently served as an Advisor to the CLSI Antimicrobial Susceptibility Testing Sub-Committee, is a current member of the CLSI AST Resistance Working Group and the Methods Application and Interpretation Working Group. She is also an active member of the Board of Scientific Councilors for the Office of Infectious Diseases of the Centers for Disease Control and Prevention. Dr. Sharp is a Past-President of ASM and a former member of ASM’s Board of Directors. Dr. Sharp has given numerous lectures, seminars and workshops locally, nationally and internationally, and has numerous publications in the field of clinical microbiology. Her most prominent area of interest has centered on cost-effective, clinically-relevant diagnostic microbiology.
What is eNat®?
COPAN’s eNat® system is intended for the collection and preservation of upper respiratory tract specimens. The sample collection system completely stabilizes and renders the sample non-infectious within minutes. eNat® has been FDA cleared for use in the detection of influenza A viruses (REF: FDA KK201849). eNat® is a versatile system combining a COPAN flocked swab with a guanidine-thiocyanate based medium to stabilize RNA and DNA of viruses and bacteria.
How is eNat® Used?
eNat® securely handles specimens that may contain highly infectious agents, such as SARS-CoV-2, using a detergent and a protein denaturant to completely inactivate microbial viability within minutes. Nuclease inactivation provided by eNat® ensures the integrity of the target sequences, while protecting polynucleotides against exposure to DNases and RNases. Specimens preserved in eNat® can be stored for up to four weeks at 4oC or at -20°C for up to six months. eNat® medium has been shown to inactivate influenza A virus in 10 seconds and preserve influenza A virus RNA for up to 4 weeks stored at 2-25°C when tested with the Cepheid Xpert Xpress Flu/RSV Assay. COPAN eNAT® is specifically indicated as a suitable sample collection kit for nasopharyngeal and anterior nasal swab samples for the Cepheid assay. eNAT® collection kits are widely available on the market. Other molecular assays and methods may also be applicable for use with eNAT® with prior validation.
Scientific Review of Publications
Several studies have evaluated at the use of eNat® when testing samples for SARS-CoV-2 virus, to evaluate its biosafety and possible expansion of testing to point-of-care and more remote, in-field, areas.
A study by a Banik et. al. showed that when using SARS-CoV-2 virus spiked directly into eNat®, the virus could be inactivated at a concentration of >5.6 log10 PFU/ml within one minute of incubation. When testing saliva diluted 1:1 in eNat® no cytopathic effect (CPE) in cell culture was observed, although viral RNA could still be detected even after two cell culture passages. A 1:2 saliva/eNat® dilution was also shown to abrogate CPE in as little as 5 minutes of incubation. SARS-CoV-2 RNA from virus spiked at 5X the limit of detection of their assay platform remained positive for up to 7 days in all storage conditions tested. The authors concluded that eNat® is of value for the transport, stabilization, and processing of clinical samples for molecular testing of SARS-CoV-2.
Another study by Richard-Greenblatt et. al. demonstrated that high-titer SARS-CoV-2 placed into eNat® medium cannot be propagated in cell culture showing viral inactivation. They also assessed the stability of contrived nasopharyngeal specimens stored for up to 14 days in various transport media and temperatures. The molecular detection of SARS-CoV-2 was unaffected by sample storage temperature over the 2 weeks when stored in eNat® at 4°C, 22 to 25°C, and 35°C. In contrast, variable stability was observed across test conditions for the other transport media evaluated. Noting that eNat® can inactivate SARS-CoV-2, the authors state that eNat® supports COVID-19 diagnostics at point of care, is compatible the Cepheid Xpert Xpress SARS-CoV-2 assay and showed diagnostic accuracy and sensitivity equivalent to that of VTM. The authors conclude that their findings suggest that the implementation of eNat® as a collection device can expand COVID-19 testing to areas with limited health care access.
In addition, the study by van Bockel et. al. determined that the use of eNat® as a first step after specimen collection will render SARS-CoV-2 non-infectious for transport, or for further in-field point of care molecular testing allowing for rapid turnaround times in the GeneXpert® or equivalent platforms.
When comparing eNat® to viral transport medium (VTM) the study of Banada et. al. evaluated the diagnostic yield across different non-invasive specimen types. They demonstrated that swab specimens collected in eNat® showed an overall superior sensitivity compared to swabs collected in VTM (70% vs 57%) and that saliva specimens collected in eNat® were significantly more sensitive than nasal or oral swabs in VTM. The authors concluded that saliva with the use of eNat® increased detection of SARS-CoV-2 and can enhance safe and sensitive detection of COVID-19 using point of care instruments.
Together these independent studies confirm that eNat® can be used for the safe collection and transportation, and sensitive detection, of the SARS-CoV-2 virus at both point of care and in-field rural settings.
How to Get eNat®
COPAN’s eNat is available in three configurations and can be purchased thru our distribution partner Fisher Scientific.
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