Boston: A review of studies has found major weaknesses in the evidence base for diagnostic accuracy of COVID-19 antibody tests, particularly for point-of-care tests performed directly with a patient, outside a laboratory, and does not support their continued use.
Serological tests to detect antibodies against COVID-19 could improve diagnosis and may be useful tools for monitoring levels of infection in a population, but it is important to formally evaluate whether there is sufficient evidence that they are accurate, the researchers said.
The study, published n The BMJ, set out to determine the diagnostic accuracy of antibody tests for COVID-19. The researchers, including those from Harvard Medical School in the US and University of British Columbia, Canada, searched medical databases and preprint servers from January 1 to April 30, for studies measuring sensitivity and specificity of a COVID-19 antibody test compared with a control test.
Sensitivity measures the percentage of people who are correctly identified as having a disease, while specificity measures the percentage of people who are correctly identified as not having a disease, they said. Of 40 eligible studies, most (70 per cent) were from China and the rest were from the UK, US, Denmark, Spain, Sweden, Japan and Germany.
The researchers noted that half of the studies were not peer-reviewed and most were found to have a high or unclear risk of bias -- problems in study design that can influence results. Only four studies included outpatients and only two evaluated tests at the point of care, they said.
When sensitivity results for each study were pooled together, they ranged from 66 per cent to 97.8 per cent depending on the type of test method used, meaning that between 2.2 per cent and 34 per cent of patients with COVID-19 would be missed, according to the researchers.
Pooled specificities ranged from 96.6 to 99.7 per cent, depending on the test method used, meaning that between 3.4 per cent and 0.3 per cent of patients would be wrongly identified as having COVID-19, they said. The study found that pooled sensitivities were consistently lower for the lateral flow immunoassay (LFIA) test compared with other test methods.
The LFIA test is the potential point-of-care method that is being considered for 'immunity passports. The researchers explained that, if an LFIA test is applied to a population with a COVID-19 prevalence of 10 per cent, for every 1,000 people tested, 31 who never had COVID-19 will be incorrectly told they are immune, and 34 people who had the disease will be incorrectly told that they were never infected.
Pooled sensitivities were also lower with commercial test kits (65 per cent) compared with non-commercial kits (88.2 per cent) and in the first and second week after symptom onset compared with after the second week, they said. The researchers point to some limitations, such as differences in study populations and the potential for missing studies. However, study strengths include thorough search strategies and assessment of bias, they said.
"These observations indicate important weaknesses in the evidence on COVID-19 serological tests, particularly those being marketed as point-of-care tests," the researchers said. "While the scientific community should be lauded for the pace at which novel serological tests have been developed, this review underscores the need for high-quality clinical studies to evaluate these tools," they added.
"This is a detailed and thorough assessment of antibody tests that were developed and published in the first few months of the pandemic," said Sanjeev Krishna, Professor at St George's, University of London.
"Like most diagnostic tests that need to be developed with urgency, the first products may lack robustness through poor evaluation methodologies or poor test performance, but many tests can be improved with time," said Krishna, who was not involved in the study. He noted that it is important not to dismiss them from the start, as antibody tests will take their place in the suite of diagnostic tests that are needed to understand and manage the COVID-19 pandemic.
Alexander Edwards, Associate Professor at the University of Reading said some important points are highlighted in the study about the way that antibody tests are validated or evaluated. For example, he said, the accuracy that any study publishes will depend a lot on the population used.
"Many studies are incomplete because they select only very specific groups of samples. But it takes time and a lot of resources to collect all different types of sample needed to fully define the performance of an antibody test," Edwards added.
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United Nations (PTI): A spokesperson for UN Secretary-General Antonio Guterres has said the world body "hopes" that in India and any country that is having elections, people's "political and civil rights" are "protected" and everyone is able to vote in a "free and fair" atmosphere.
Spokesperson for the Secretary-General Stephane Dujarric made these remarks on Thursday while he was responding to a question on the "political unrest" in India ahead of the upcoming national elections in the wake of the arrest of Delhi Chief Minister Arvind Kejriwal and the freezing of the opposition Congress Party's bank accounts.
"What we very much hope that in India, as in any country that is having elections, that everyone's rights are protected, including political and civil rights, and everyone is able to vote in an atmosphere that is free and fair," Dujarric said at the daily press briefing Thursday.
The response from the United Nations comes a day after the US also reacted to a similar question on Kejriwal's arrest and freezing of the Congress party's bank accounts.
On Wednesday, hours after India summoned a senior US diplomat to protest remarks on Kejriwal's arrest, Washington reiterated that it encourages fair, transparent, timely legal processes.
On the US diplomat being summoned in Delhi, US State Department Spokesperson Matthew Miller said "I'm not going to talk about any private diplomatic conversations. But of course what we have said publicly is what I just said from here, that we encourage fair, transparent, timely legal processes. We don't think anyone should object to that, and we'll make the same thing clear privately."
Ministry of External Affairs (MEA) officials summoned Acting Deputy Chief of Mission Gloria Berbena to their office in South Block in the Indian capital. The meeting lasted for more than 30 minutes.
On Thursday, India said the US State Department's recent remarks on the arrest of Delhi Chief Minister Arvind Kejriwal are "unwarranted" and asserted the country is "proud of its independent and robust democratic institutions" and committed to protect them from any form of undue external influences.
Any "external imputation" on India's electoral and legal processes is "completely unacceptable", MEA Spokesperson Randhir Jaiswal said in New Delhi during his weekly press briefing.
In India, legal processes are driven "only by the rule of law", Jaiswal said on Thursday.
Earlier on Wednesday, the Ministry of External Affairs (MEA) had said in a statement that India took strong objection to the remarks of the Spokesperson of the US State Department about certain legal proceedings in India.
"India's legal processes are based on an independent judiciary which is committed to objective and timely outcomes. Casting aspersions on that is unwarranted," the MEA had said.
The Enforcement Directorate has arrested Kejriwal in a money laundering case linked to the excise policy 'scam'.
The case pertains to alleged corruption and money laundering in formulating and executing the Delhi government's excise policy for 2021-22 which was later scrapped.