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There is wide variation in the performance of commercial kits for detecting antibodies to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), according to a study published Sept. 24 in the open access journal. PLOS Pathogens by Jonathan Edgeworth and Blair Merrick of Guy’s and St Thomas’ NHS Foundation Trust, Suzanne Pickering and Katie Doores of King’s College London, and colleagues. As the authors noted, rigorous comparison of antibody testing platforms will inform the deployment of point-of-care technologies in healthcare settings and their use in monitoring SARS-CoV-2 infections.
Nose and throat swab tests for SARS-CoV-2 establish whether someone is infected with the virus that causes coronavirus disease 2019 (COVID-19). These tests are very sensitive, capable of detecting very low levels of viral RNA, and are optimal for early detection of the virus. The performance of these tests depends on when the sample is collected, and the viral load decreases after the first week of symptoms. Rather, antibody tests can determine if someone has had the virus in the past. For later diagnosis in disease or late-onset syndromes, antibody testing could form an important part of the hospital’s diagnostic capabilities. In the new study, the researchers developed their own sensitive and specific antibody assay and used it to make direct and unbiased comparisons of ten commercial antibody test kits on an identical panel of 110 SARS-CoV-2 positive blood samples. of patients admitted to hospitals with COVID-19 and 50 pre-pandemic negatives.
There was a wide range of performance between tests, with specificity: the ability of the test to correctly identify those without the disease (true negative rate), ranging from 82% to 100%, and the overall sensitivity: a test to correctly identify people with the disease (true positive rate), which ranges from 60.9% to 87.3%. But all gave the best results when used 20 days or more after the onset of symptoms, and most of the tests reached a sensitivity value greater than 95%. Furthermore, antibody levels were higher in individuals with severe disease compared to those with mild or asymptomatic disease. When all commercial tests were compared, lateral flow immunoassays called Accu-Tell, SureScreen and Spring demonstrated the highest sensitivity at earlier time points, while maintaining specificities of 98% or more. Such lateral flow immunoassays are affordable, fast and easy to use and, if properly implemented, could be of considerable utility in healthcare settings.
Co-author Jonathan Edgeworth notes: “We found that some of the Rapid Single Use Kits (LFIAs) are as accurate as our sophisticated laboratory technologies. Encouraged by these findings, we are testing LFIAs in the hospital to give clinicians a rapid response. and reliable in a variety of clinical settings. “
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