First-in-Class Study Validates Alternate Transport Media and Broader Storage Conditions for SARS-CoV-2 (COVID-19) Testing on RT-PCR Platforms
May 1, 2020
SARS-CoV-2 (COVID-19) is a communicable illness caused by a newly identified coronavirus with the number of clinical cases currently on the rise globally. Since the first reported case in December 2019, greater than 3.2 million cases have been reported worldwide as of April 30, 2020 . As the emergent COVID-19 pandemic intensifies, the heavy demand for testing and treatment has put an unprecedented burden on medical professionals, laboratory staff, and medical supply chains. Protocols concerning proper COVID-19 sampling, transport, and testing methods are rapidly evolving, and global research initiatives are underway to improve these practices and increase testing capacity.
The Food and Drug Administration (FDA) and the Centers for Disease Control & Prevention (CDC) currently recommend the gold standard of upper respiratory viral specimen collection and transport using nasopharyngeal flocked swabs in viral transport media. However, the rapidly growing COVID-19 pandemic has severely burdened laboratory supply chains causing shortages in many of these essential testing supplies, limiting short-term testing capacity. To meet the increasing demand, the FDA and CDC recently changed the guidelines to allow additional sampling sites, and additional swab types and materials. They also expanded the acceptable transport media to include alternates like liquid amies and phosphate-buffered saline (PBS) media stored at 4℃ for up to 72 hours or frozen at ≤ -70℃ for longer-term storage [2,3].
Studies on SARS-CoV-2 stability in the environment and in various transport media and conditions are very limited at this time. However, stability studies for other similar, but more established RNA enveloped viruses, such as influenza, rubella, enterovirus, herpes simplex virus, and adenovirus suggest that the stability of COVID-19 may allow for a broader set of transport media and environmental conditions than currently outlined.
A timely new study, titled “Evaluation of Transport Media and Specimen Transport Conditions for the Detection of SARS-CoV-2 Using Real-Time Reverse Transcription PCR” published in the Journal of Clinical Microbiology (JCM) investigated the stability of SARS-CoV-2 virus RNA preserved in multiple specimen transport media under various storage temperatures for RT-PCR testing. The study tested several transport media including:
- VCM (Copan, Brescia, Italy)
- UTM®-RT (Copan, Brescia, Italy)
- ESwab™(Copan, Brescia, Italy)
- M4 media (Thermo Fisher Scientific, Waltham, MA)
- Normal Saline [0.9% NaCl].
Nasopharyngeal/Oropharyngeal (NP/OP) swabs were taken and stored in the above transport media, as well as bronchoalveolar lavage (BAL), and sputum. Samples were aliquoted and stored for up to 14 days and tested at multiple time points and storage temperatures from (18°C to -30°C). Five aliquots were assayed using PCR detection at each condition. The study also included additional viral stability testing at a separate facility (Quest Diagnostics Marlborough, MA) of spiked samples stored in saline. Aliquots of these saline samples were likewise stored at various temperatures (18°C to -30°C) and then tested at time points up to 14 days. For all samples tested, a high-titer SARS-CoV-2 remnant patient specimen was spiked into pooled SARS-CoV-2 RNA-negative specimen remnants for the various media types.
The results of the study indicated that SARS-CoV-2 RNA was consistently detected in all transport media, specimen types, and storage conditions tested; mean Ct values obtained for SARS-Cov-2 for the various study-defined transport media and storage temperatures are shown in the tables below.
The study also observed that specimens consistently yielded amplifiable RNA with mean Ct differences of <3 over the various conditions assayed, thus supporting the use of alternative media for transport and specimen types under a variety of temperature storage conditions. Qualitative detection of SARS-CoV-2 RNA was unchanged over the various combinations of transport media and conditions tested at two study sites regardless of the molecular platform utilized.
Additionally, specimen stability was assessed for a significantly longer duration than would be deemed acceptable for routine clinical testing, further reducing the probability of clinical impact. These data provide additional supporting evidence for the use of alternative viral transport media and temperature storage conditions for the detection of SARS-CoV-2 RNA using sensitive rRT-PCR assays.
As COVID-19 infection rates continue to rise and mass testing requirements for communities and municipalities increase, demand for COVID-19 testing and transport will likely continue to grow for the foreseeable future. Studies like this one published recently in JCM that validate alternate methods and materials for the collection, transport, and preservation of COVID-19 specimens are essential in increasing testing capacity. Read the full study here.
- Center for Systems Science and Engineering at John Hopkins University. (2020, April 30). COVID-19 dashboard. Retrieved April 30, 2020, from https://www.arcgis.com/apps/opsdashboard/index.html#/bda7594740fd40299423467b48e9ecf6
- Centers for Disease Control and Prevention. (2020, February 14). Coronavirus Disease 2019 (COVID-19): Guidelines for Clinical Specimens. Retrieved April 30, 2020, from https://www.cdc.gov/coronavirus/2019-nCoV/lab/guidelines-clinical-specimens.html
- Food and Drug Administration. (2020, April 29). FAQs on Diagnostic Testing for SARS-CoV-2. Retrieved April 30, 2020, from https://www.fda.gov/medical-devices/emergency-situations-medical-devices/faqs-diagnostic-testing-sars-cov-2