Mean time of serological testing from last exposure to an index case was 714 days (IQR 560C870; figure 1). RT-PCR, performance of RT-PCR over the course of infection, and characteristics of individuals who were seropositive on total antibody ELISA but RT-PCR negative. Findings Between April 12 and May 4, 2020, we enrolled and collected serological samples from 2345 (530%) of 4422 RT-PCR-negative close contacts of cases of RT-PCR-confirmed SARS-CoV-2. 1175 (501%) of 2345 were close contacts of cases diagnosed in Shenzhen with contact tracing details, and of these, 880 (749%) had serum samples collected more than 2 weeks after exposure to an index case and were included in our analysis. 40 (45%) of 880 RT-PCR-negative close contacts were positive on total antibody ELISA. The seropositivity rate with total antibody ELISA among RT-PCR-negative close contacts, adjusted for assay performance, was 41% (95% CI 29C57), which was significantly higher than among individuals residing in neighbourhoods with no reported cases (00% [95% CI 00C11]). RT-PCR-positive individuals were 80 times (95% CI 53C127) more likely to report symptoms than those who were RT-PCR-negative Anamorelin Fumarate but seropositive, but both groups had a similar distribution of sex, age, contact frequency, and mode of contact. RT-PCR did not detect 48 (36% [95% CI 28C44]) of 134 infected close contacts, and false-negative rates Anamorelin Fumarate appeared to be associated with stage of infection. Interpretation Even rigorous RT-PCR testing protocols might miss a substantial proportion of SARS-CoV-2 infections, perhaps in part due to difficulties in determining the timing of testing in asymptomatic individuals for optimal sensitivity. RT-PCR-based surveillance and control protocols that include rapid contact tracing, universal RT-PCR testing, and mandatory 2-week quarantine were, nevertheless, able to contain Anamorelin Fumarate community spread in Shenzhen, China. Funding The Bill & Melinda Gates Foundation, Special Foundation of Science and Technology Innovation Strategy of Guangdong Province, and Key Project of Shenzhen Science and Technology Innovation Commission. Introduction Virological detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) through RT-PCR is the gold standard for diagnosing infection.1 Almost all diagnostic testing for COVID-19 is done using PCR-based methods. Like all virological tests, RT-PCR has imperfect sensitivity,2, 3, 4 and patterns of viral shedding mean that the chance of testing positive varies over the course of infection.5, 6 Hence, Rabbit Polyclonal to RPS20 although RT-PCR might be highly accurate at identifying those who are currently infectious, individuals must be tested at the right time during their infection to be detected, which reduces the utility of virological testing for measuring overall SARS-CoV-2 incidence. Serological tests offer an alternative approach for detecting SARS-CoV-2 infection by measuring circulating antibodies against the virus. By contrast with virological tests, serological tests can detect if an individual has been infected even months after viral clearance, though serological tests also have imperfect sensitivity and specificity.7 By utilising both tests in the same population, we can gain an understanding of the practical performance of RT-PCR-based surveillance, if three conditions are met. First, virological RT-PCR surveillance must have occurred around Anamorelin Fumarate the time of potential exposure in the population. Second, the same individuals tested by RT-PCR must later receive serological tests. Third, there must be a low chance of infection between the periods of virological and serological surveillance. Research in context Evidence before this study We searched PubMed on Sept 3, 2020, with no date or language restrictions, using the keywords serology AND PCR AND SARS-CoV-2, and found two articles that reported serological testing in a cohort of individuals who had been tested with RT-PCR..