Abstract
The COVID-19 pandemic is an ongoing global pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in 2020–2021. COVID-19 is becoming one of the most fatal pandemics in history and brings a huge challenge to the global healthcare system. Opportune detection, confinement, and early treatment of infected cases present the first step in combating COVID-19. Diagnosis via viral nucleic acid amplification tests (NAATs) is frequently employed and considered the standard procedure. However, with an increasing urge for point-of-care tests, rapid and cheaper immunoassays are widely utilized, such as lateral flow immunoassay (LFIA), which can be used for rapid, early, and large-scale detection of SARS-CoV-2 infection. In this narrative review, the principle and technique of LFIA applied in COVID-19 antigen and antibody detection are introduced. The diagnostic sensitivity and specificity of the commercial LFIA tests are outlined and compared. Generally, LFIA antigen tests for SARS-CoV-2 are less sensitive than viral NAATs, the “gold standard” for clinical COVID-19 diagnosis. However, antigen tests can be used for rapid and mass testing in high-risk congregate housing to quickly identify people with COVID-19, implementing infection prevention and control measures, thus preventing transmission. LFIA anti-SARS-CoV-2 antibody tests, IgM and/or IgG, known as serology tests, are used for identification if a person has previously been exposed to the virus or vaccine immunization. Notably, advanced techniques, such as LFT-based CRISPR-Cas9 and surface-enhanced Raman spectroscopy (SERS), have added new dimensions to the COVID-19 diagnosis and are also discussed in this review.
Highlights
Diagnostics 2021, 11, 1760 than 10 million [20,21]
The results showed that detection of nucleocapsid antibody to SARS-CoV-2 is more sensitive than antibody to spike protein in COVID-19 patients [74]
The authors concluded that the sensitivity range of the commercial SARSCoV-2 rapid POC antigen tests was closely related to SARS-CoV-2 viral loads observed in the first week of symptoms, which marks the infectious period in most patients
Summary
Molecular tests for COVID-19 are generally divided into two types: viral and antibody testing [50,51]. NAATs detect and identify genetic material, i.e., viral RNA, of SARS-CoV-2. The standard COVID-19 test is a quantitative real-time polymerase chain reaction (qRT-PCR), i.e., NAATs [56], which detects the presence of viral RNA. WHO has published several testing protocols based on nucleic acid for the disease [58] As these tests detect viral RNA, i.e., qRT-PCR test, the qRT-PCR tests require hours before their results are available [56], special equipment is vital, and the tests are relatively more expensive. It could be difficult to develop a point-of-care (POC) version of the qRT-PCR test Proper interpretation of both antigen test and NAATs results is important for accurate clinical management of COVID-19 patients or people who are suspected of being infected and for identification of infected people when used for screening. It may be necessary to confirm an antigen test result with medical- or laboratorybased NAATs, especially if the results of the antigen tests are inconsistent with the clinical context [53]
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