However, provisions were made to be able to “bridge” to related instrumentation if a laboratory could prove through paired sample analysis that the accuracy was not negatively affected. In essence, any deviation, including use of alternate thermal cyclers or extractors, negated the authority granted by the EUA. The EUA process prescribes exactly how an assay must be performed in order to maintain regulatory compliance. The first EUA was issued on to the CDC and was accessible to clinical laboratories after February 29, 2020. This review process served to grant the applicant with an Emergency Use Authorization or EUA. The FDA authorization allowed any clinical or commercial laboratory operating under the Clinical Laboratory Improvements Amendment of 1988 (CLIA ’88) to develop and provide clinical testing following review by the FDA. In response to a variety of external pressures and the impending community-wide spread of SARS-CoV-2, on February 29, 2020, the FDA authorized local clinical and commercial laboratories to develop and use qualified molecular methods for the diagnostic detection of SARS-CoV-2. Molecular testing and the FDA emergency use authorization Interestingly, many of the molecular diagnostic assays available today contain targets that do not distinguish between SARS-CoV-2, MERS-CoV, and SARS-CoV however, with the understanding that SARS-CoV has been eradicated and the outbreaks of MERS-CoV have been geographically and clinically limited, these assays are effectively only identifying SARS-CoV-2. Second, since antibody production is a hallmark of an appropriate immune response following infection, serological testing also needs to distinguish between commonly circulating seasonal strains versus the pandemic strain. First, since these viruses are highly related, molecular targets need to differentiate between the various pathogens. The distinction between SARS-CoV-2 and the seasonal coronaviruses is important in terms of diagnostics for several reasons. Two other seasonal viruses, 229E and NL63, are members of the alphacoronavirus genera and together these two genera comprise all of the coronaviruses known to infect humans. Other members of this genera include Middle East respiratory syndrome coronavirus (MERS-CoV), severe acute respiratory syndrome coronavirus (SARS-CoV, 2002-3 strain), and the seasonal coronavirus strains OC43 and HKU1 ( Fig. 1 SARS-CoV-2 is an enveloped virus with a single-stranded RNA genome belonging to the betacoronavirus genera. Both molecular and serological testing for SARS-CoV-2 have complementary roles in patient management, and we highlight the challenges faced by clinicians and laboratorians alike in the evaluation and interpretation of the currently available laboratory assays.Ĭoronavirus disease 2019 or COVID-19 is caused by the SARS-CoV-2 virus. Serological tests have multiple assay formats, detect various classes of immunoglobulins, and have a distinct role in seroprevalence studies however, the association with long-term protection remains unclear. While SARS-CoV-2 assays can suffer from poor sensitivity, all FDA authorized assays to date are intended to be qualitative. This leads to some confusion among clinicians as to which test to order and when each is appropriate. In contrast, serological testing is typically performed once viral RNA has been cleared and symptoms have resolved. Molecular detection of SARS-CoV-2 is the only diagnostic test currently available in acutely or recently infected individuals. Laboratory evaluation of SARS-CoV-2 involves the detection of viral nucleic acid, viral protein antigens, and the antibody response.
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