Nasopharyngeal (NP) swabs are the preferred specimen type for COVID-19 per the Centers for Disease Control and Prevention (CDC), but this topic is rapidly evolving. Microbiology dogma dictates that good specimen collection leads to accurate results from the lab, but we aren't even sure what "good specimen collection" means for COVID-19. Variables in Specimen Collection and Transport These variables could help explain why some SARS-CoV-2 tests are negative when in fact, the patient has clinical disease. We are learning something new every day about the best specimen types, collection methods and testing platforms for SARS2-CoV detection. For RT-PCR tests, like those used to diagnose COVID-19, false negatives occur for a variety of reasons, such as the level of viral RNA being below the limit of detection of the test. 'False-negative' test results refer to cases where someone who truly has the disease tests negative instead of positive.
What Factors Influence Test Performance & Could They Cause False-Negative Results? While these protocols do not overcome the test performance uncertainty explored below, they do enable labs to establish that tests work to the manufacturer's specifications within that specific testing environment. ASM has published protocols for clinical laboratories to help them verify commercial SARS-CoV-2 kits. When we last checked (April 24th, 2020), there were 45 commercial COVID-19 test kits and 10 laboratory-developed tests (tests uniquely developed by the performing laboratory) that have received FDA EUA approval. The overall performance of SARS-CoV-2 RT-PCR tests cannot be known until we understand who is truly infected and who isn't.
However, these analyses differ in meaning from clinical sensitivity and specificity (the percentage of positive patients who test positive and negative patients who test negative, respectively) and a test with good analytical sensitivity and specificity does not necessarily have good clinical sensitivity and specificity. Analytical sensitivity is the smallest amount of substance in a sample that can be reliably detected by an assay (limit of detection) and analytical specificity is the assay's ability to detect only the desired substance in a sample without cross reacting with other substances. The FDA's EUA templates require analytic sensitivity and specificity analyses. Clinical and commercial laboratories, as well as test kit manufacturers, may therefore submit expedited submissions for FDA EUAs of their diagnostic devices and assays. 4, 2020, the Human Health and Services (HHS) Secretary determined that there is a public health emergency, and therefore, circumstances justify the emergency use authorization (EUA) of in vitro diagnostics for the detection and/or diagnosis of SARS-CoV-2, the virus that causes COVID-19. Since the test is new, its performance needs to be compared to the performance of a current "gold-standard" test, also known as the "reference standard." There currently is no gold-standard diagnostic test for SARS-CoV-2 since the virus is new to us. In the cases where a new diagnostic panel is developed but can be used on existing equipment (the Centers for Disease Control and Prevention's SARS-CoV-2 assay, for example), a relatively lengthy FDA review may still be required under normal conditions (e.g. If the test is innovative, clinical studies are typically required to demonstrate adequate performance of the test.
BRIDGE DIAGNOSTICS PCR TEST RESULTS SERIES
If a company wants to sell a new diagnostic testing platform, they normally have to endure a series of steps including test classification, applications and paying fees. Generally, lab tests are classified as in vitro diagnostics (IVD) by the Food and Drug Administration (FDA) and go through a rigorous approval process to gain FDA clearance. Caveat: evolving! What Tests Are Available for COVID-19 and How Are They 'Approved' in the U.S.? We break down some of the major challenges of SARS-CoV-2 testing, including issues of test performance and interpretation, to give these reports context. Now that COVID-19 diagnostics are available in most of the United States, media reports are surfacing about false-negative test results and the possibility of reinfection.
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