The 2019 coronavirus outbreak (COVID-19), caused by the acute acute coronavirus 2 (SARS-CoV-2) respiratory syndrome, first appeared in Wuhan, China, in December 2019. Since then it has spread to 192 country and regions, suffering more than 100 million people and claiming more than 2.2 million lives. To date, Japan has reported 391,945 cases and 5,833 deaths.
A team of researchers in Japan has developed commercially available antibody tests to estimate the prevalence of SARS-CoV-2 infection in a population. Given the importance of this in pandemic management policies, cost-effective and efficient seroprevalence testing methods can help manage local and national outbreaks.
The study, published in the U.S. Centers for Disease Control and Prevention (CDC) Emerging infectious diseases journal, demonstrating the use of reliable joint experiments as an effective way to assess seroprevalence in low-frequency conditions. Seroprevalence is low in Japan, demonstrating the country’s success in preventing the spread of the virus.
The study
The study highlights the importance of antibody testing in countries affected by coronavirus pandemic. Because many COVID-19 individuals may have no symptoms at all, some people may be infected without misunderstanding it.
Antibody testing can help the government and public health authorities determine the extent of the pandemic in a particular region or country. This can help design health policies and measures to prevent further infection.
Countries with low seroprevalence are at higher risk for a second wave of diseases, as this lack of herd immunity allows transmission chains to multiply.
The researchers used two commercially available antibody tests to detect the nucleocapside antigen SARS-CoV-2, including Abbott’s SARS-CoV-2 IgG immunoassay, microparticle chemiluminescent immunoassay, and Hoffman-La Roche’s Elecsys Anti-SARS-CoV-2 immunoassay, an electrochemiluminescence immunoassay.
To reach the conclusions of the study, the team performed a seroprevalence study on COVID-19 disease in three prefectures in Japan between June 1 and 7, 2020. The researchers selected two predictions with a relatively high frequency of COVID cases -19 from May 31, 2020. These include Tokyo and Osaka. To compare the results, the team also selected a low-frequency prefecture, namely Miyagi, Japan.
All eligible participants in all prefectures were older than 20 years and had no symptoms of SARS-CoV-2 infection. They completed a questionnaire before health care professionals collected blood samples. From there, the researchers collected serum and tested these samples using both antibody tests.
The positive or negative boundary samples were sent to the Japan National Institute of Infectious Diseases for a neutral antibody assay with VeroE6 or TMPRSS2 cells.
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In total, 13,547 people were invited to take part in the study. However, only 7,950 agreed to participate. Of these, eight were seropositive in each, meaning that they had previously maintained SARS-CoV-2 and developed antibodies against it. However, 30 samples tested positive with just one test, 15 each for Abbott and Roche tests.
Despite some positive tests for just one test, only eight samples that were positive for each commercial test were also positive for antibody assay neutralization. The results of the study showed that two positive test results correctly identified seropositive participants.
The team concluded that both commercial experiments with high sensitivity and specificity would be appropriate for use to determine the extent of the pandemic in a particular area.
We estimate that seroprevalence of SARS-CoV-2 ranged from 0.03% –0.17% in Japan in early June 2020. Public health officials in low-frequency areas should consider using 2 antibody tests in conjunction for proper analysis. ”
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