Serodiagnostics for Severe Acute Respiratory Syndrome–Related Coronavirus 2

Abstract

Accurate serologic tests to detect host antibodies to severe acute respiratory syndrome-related coronavirus-2 (SARS-CoV-2) will be critical for the public health response to the coronavirus disease 2019 pandemic. Many use cases are envisaged, including complementing molecular methods for diagnosis of active disease and estimating immunity for individuals. At the population level, carefully designed seroepidemiologic studies will aid in the characterization of transmission dynamics and refinement of disease burden estimates and will provide insight into the kinetics of humoral immunity. Yet, despite an explosion in the number and availability of serologic assays to test for antibodies against SARS-CoV-2, most have undergone minimal external validation to date. This hinders assay selection and implementation, as well as interpretation of study results. In addition, critical knowledge gaps remain regarding serologic correlates of protection from infection or disease, and the degree to which these assays cross-react with antibodies against related coronaviruses. This article discusses key use cases for SARS-CoV-2 antibody detection tests and their application to serologic studies, reviews currently available assays, highlights key areas of ongoing research, and proposes potential strategies for test implementation.

Laboratory testing for the diagnosis of COVID-19

“…Serologic tests are less likely to be reactive in the first several days to weeks of infection, they have very limited utility for diagnosis in the acute setting [ 62 , 63 ]. If used, checking serology three to four weeks after the onset of symptoms optimizes the accuracy of testing [ 58 ].…”

Strategic Anti-SARS-CoV-2 Serology Testing in a Low Prevalence Setting: The COVID-19 Contact (CoCo) Study in Healthcare Professionals

“…SARS-CoV-2-specific B cell responses typically lead to detectable antibody titers and fully positive rates at about 18 days after the initial onset of symptoms [11]. Seroepidemiological studies can help to catalogue those who have been previously infected (including mild or subclinical infections) and may help identify atrisk populations [12]. Longitudinal analysis of humoral immunity is particularly valuable in persons at high risk for exposure such as HCP.…”

Rheumatology practice amidst the COVID-19 pandemic: a pragmatic view

“…56 As serological assays become available, patients and HCWs can be tested to identify those who have developed an immunological response. 57 This may include the identification of cases of asymptomatic infection or false-negative RT-PCR. 57– 59 While it is expected that most COVID-19 patients develop some kind of immune response, it has been shown that antibody titres can be of limited magnitude in up to 30% of cases and absent in up to 6%.…”

“…57 This may include the identification of cases of asymptomatic infection or false-negative RT-PCR. 57– 59 While it is expected that most COVID-19 patients develop some kind of immune response, it has been shown that antibody titres can be of limited magnitude in up to 30% of cases and absent in up to 6%. 60 Also, it is not clear if existing IgG antibodies are always protective, at what titre, and for how long.…”

“…60 Also, it is not clear if existing IgG antibodies are always protective, at what titre, and for how long. 56 57 Nor is it known if the severity of infection influences the degree of immune response. 25 61 The impact of other factors such as age, sex, comorbidities and concomitant immunosuppressive therapy is also completely unknown and may play a role in patients with RMDs.…”