Nature antibody test sits far more than official statistics

MAY 15, 2020/PRNEWSWIRE
/BIOON, CALIFORNIA, A COUNTY WHERE EXTENSIVE ANTIBODY TESTING HAS SHOWN A MUCH HIGHER INFECTION RATE THAN OFFICIAL DATA SUGGESTThe results also show that the lethality rate of the virus is lower than current estimates of global cases and deathsBut some scientists have raised concerns about the accuracy of the kits used in such studies, as most do not undergo rigorous evaluation to confirm their reliabilityIn early April, a blood analysis of about 3,300 people in Santa Clara County found that one in 66 people was infected with SARS-CoV-2On the basis of the findings, the researchers estimate that about 48,000-82,000 people in the 2 million inhabitants were infected with the virus, compared with 1,000 officially reported at the timethese results are one of the first results of more than a dozen "serological epidemiological surveys" conducted in cities around the world, in the absence of extensivediagnostictests, to estimate the true infection rate of the populationThe World Health Organization is also conducting a global serological epidemiological study called Solidarity IIImage Source: CDCmany investigations to use commercial antibody kits to detect viral antibodies in blood samplesThe presence of SARS-CoV-2-specific antibodies suggests that a person is infected at least a week ago, even if they do not have any symptoms"The serum survey gives you a timely look at who is infected in a particular population," said Kanta Subbarao, a virologist at the Peter Doherty Institute for Infection and Immunology in Melbourne,This is especially important for infections such as SARS-CoV-2, as some people do not show any symptoms or are only mild"
combined with information on age, gender, symptoms, co-disease and socio-economic status, these surveys also help to answer questions about factors affecting, such as the role of children in the transmission of infection, and the proportion of asymptomatic cases"It's a very cheap way to get a lot of information, " said Jayanta Bhattacharya, a health economist at Stanford University in California and co-author of the studyApril 9th, Germany published preliminary results of a similar studyThe study, which tested about 500 people in a village of more than 12,000 people, found that one in seven people was infected with SARS-CoV-2The German team also useddiagnostictests based on polymerase chain reactions to look for active infection hotspots, and when combined with people with antibodies, the researchers estimated the town's overall infection rate at 15 percent, says Virologist Christian Drosten, director of the Institute of Virology at The University Hospital of Berlin, but the results may not explain what is happening in Germany as a whole, as many people in the city celebrate the carnival in February"There was a big explosion in that village," he saidPeter Collignon, a doctor and microbiologist at the Australian National University in Canberra,, said it was not surprising that the two studies had a much higher infection rate than official figuresThe virus has been circulating in parts of the United States and Europe for at least a month and is then found to be circulating in the communityBut Collignon noted that the commercial antibody tests used in both studies were evaluated in a minority, which may also affect the accuracy of the findingsantibody kits are not only used in population studiesKits are also on the market to detect whether an individual has the diseaseBut experts warn that most tests are not rigorously evaluated to ensure their reliabilityHow deadly is SARS-CoV-2? serum survey can also use infection fatality (IFR) to better estimate the fatality of the virus, i.e the proportion of all infections that cause death, not just those that have been identified through clinical trials " an accurate IFR could improve the model used to determine public health responses If a disease is less deadly than previously estimated, it may not be until we re-establish our coping strategies Neeraj Sood, a health economist at the University of Southern California, said he led a separate antibody study in Los Angeles and co-author of the Santa Clara study "We're trying to stop the spread of the disease, but at the same time, unemployment in the U.S is rising because of precautions, so there's a trade-off," he said The Santa Clara team estimated that the county's IFR was 0.1-0.2%, equivalent to about 100 deaths from 48,000-82,000 infections As of April 10, the official death toll in the county was 50 The ifR in the study was lower than the IFR used in the model by researchers at Imperial College London, which estimated the UK's IFR at 0.9 per cent based on Chinese data In another study, the same group estimated the IFR at 0.66 percent in China and 0.5 percent for the death on the Diamond Princess cruise ship data vary from region to region due to the age distribution of the population and the scope of detection As more people are being tested, researchers have learned more about less serious cases, such as swine flu in 2009, and mortality estimates have declined over time, said Eran Bendavid, a population health researcher at Stanford University and director of the Santa Clara Research Project concerns about tests
but scientists are concerned about the reliability of antibody tests, especially in terms of the number of false positives they produce, which could exaggerate estimates of infection rates The kit used in the Santa Clara study was purchased from Premier Biotech in Minneapolis, Minnesota According to the manufacturer's kit performance data, 2 out of 371 true negative samples were false positives But, because of the high false positive rate, 50 of the 3,300 positive cases reported in the study may be false positives, said Marm Kilpatrick, an infectious disease researcher at the University of California, Santa Cruz Michael Busch, director of the Vitalant Institute in San Francisco and an infectious disease expert, said that to ensure that the test was sensitive enough to test for a true SARS-CoV-2 infection, it was necessary to assess the number of positive CASEs of COVID-19 and thousands of negative cases But most kits have not been thoroughly tested, and health agencies are particularly concerned about the accuracy of some quick tests Researchers involved in the Santa Clara study, , said they assessed the sensitivity and specificity of antibody tests in the first 37 positive samples and 30 negative controls Tests identified 68 per cent of positive samples and 100 per cent of negative samples Bendavid said an unpublished follow-up assessment of 30 positive and 88 negative controls found that the test correctly identified 28 positive controls and 88 negative controls image source: https://cn.bing.com
Bendavid said they adjusted the performance of the test tool and the difference between the survey population and Santa Clara County to estimate the prevalence of SARS-CoV-2 in Santa Clara The proportion of white, female and wealthy participants in the survey was higher than the county's population Another potential source of bias in the study, says Kilpatrick, a , is that participants were recruited through social media As a result, he said, more people in the sample seddy people who thought they were exposed to the virus and were voluntarily tested "The true prevalence rate may be only half as high, one in ten high, and maybe even the numbers mentioned in the paper -- we don't know, because recruiting participants on Facebook presents an unknown bias," he said Bhattacharya said the results may underestimate the prevalence of the wider population because they miss people who have only recently been infected and who have not yet had an immune response, and exclude people from prisons, nursing homes and other institutions expected the results of serological epidemiological surveys conducted by other teams around the world, including China, Australia, Iceland, Italy, Germany and several others in the United States (BioValleyBioon.com) References: 1, Antibodytestsrevealttavirusinfectionsvastssvastios
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COVID-19 Antibody Seroprevalencein Santa Clara County, California 3, Willantibodytests forcoronavirus really change-changes?