Patients Investigated for COVID-19 and Tested by NAAT for SARS-CoV-2įirst, we assembled a data set of NAATs on nasopharyngeal swabs performed by the Johns Hopkins microbiology laboratory during the first month of COVID-19 testing (11 March to 12 April 2020), and tallied a total of 11 699 tests. We report the performance of a serum assay for SARS-CoV-2 spike protein, providing insights into antibody kinetics and clinical uses. Recent studies have described the technical performance of antibody assays ( 8, 18, 20–27), but data on clinical sensitivity and specificity are scarce ( 15). Cases where clinical suspicion remains high despite repeated negative NAAT results could especially benefit from serologic testing. With increased use, NAAT begins to show limitations ( 17) arising from intermittent viral shedding ( 18), time since exposure ( 19), and nasopharyngeal swab technique ( 20). These tests are predominantly performed on nasopharyngeal swabs, although samples from other anatomical sites, such as bronchoalveolar lavage, sputum, and endotracheal aspirate, are also tested. A possible use is to complement the laboratory gold standard of COVID-19 diagnosis: reverse-transcriptase polymerase chain reaction assay, commonly referred to as “nucleic acid amplification test” (NAAT). Serology facilitates assessment of prevalence in at-risk communities (such as health care workers, homeless people, and assisted living residents, among others) and the general population-a prevalence which, as demonstrated in previous viral pandemics, is typically higher than expected ( 13–16).Ĭlinical applications of COVID-19 serologic testing remain to be defined. Serologic testing for COVID-19 is considered at all levels of society for many purposes, from diagnosis and management of individual patients ( 10) to selection of convalescent patients as donors for antibody transfer to critically ill patients ( 11) and screening of blood or organ donors ( 12). Given its size, location, and essential function, spike is predicted to be a key target of antibodies ( 8, 9). Its S1 subunit mediates cell entry by binding to angiotensin-converting enzyme 2 after “priming” by transmembrane protease serine S2 ( 7). Spike is a trimeric protein that protrudes from the envelope, giving the virus its “crown” ( 6). SARS-CoV-2 is a single-stranded, positive-sense RNA, enveloped, helical virus that synthesizes 4 structural proteins: spike (S), nucleocapsid, matrix, and envelope ( 5). First reported in Wuhan, China, in December 2019, severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2) has infected 10 424 992 persons as of 30 June 2020 ( 1), causing severe disease in about 15% ( 2) and death in approximately 0.4% ( 3), due to diffuse alveolar damage featuring intra-alveolar edema and lymphoplasmacytic infiltrate ( 4). Antibodies have accompanied immunology since its inception as an academic discipline in the late 19th century (also enjoying numerous Nobel Prize recognitions), and are once more brought to center stage by the coronavirus 2019 (COVID-19) pandemic. Serum antibodies are the component of the adaptive immune system used most frequently and to greatest effect by clinicians and epidemiologists. Caturegli.Ĭollection and assembly of data: G.
Caturegli.Īdministrative, technical, or logistic support: G. Provision of study materials or patients: P. Caturegli.įinal approval of the article: G. Caturegli.Ĭritical revision for important intellectual content: G. Caturegli.Īnalysis and interpretation of the data: G. Caturegli: Johns Hopkins Pathology, Ross Building, Room 656, 720 Rutland Avenue, Baltimore, MD 21205.Īuthor Contributions: Conception and design: P. Patrizio Caturegli (e-mail, Author: Patrizio Caturegli, MD, MPH, Johns Hopkins Pathology, Ross Building, Room 656, 720 Rutland Avenue, Baltimore, MD 21205 e-mail, Author Addresses: Mr. Forms can be viewed at Reproducible Research Statement: Study protocol, statistical code, and sample data set: Available upon reasonable request to Dr. Disclosures: Authors have disclosed no conflicts of interest.