Antibody tests suspended over accuracy

India has ordered a pause in testing for antibodies to the coronavirus because of concern over the accuracy, health officials said on Wednesday.

This has complicated the fight against the epidemic as the country's tally of cases has crossed 20,000.

India trails many countries in conducting the standard swab tests to determine the presence of the novel coronavirus because of limited testing equipment and protective gear for medical workers.

Early this month, health authorities approved blood tests for coronavirus antibodies as a faster way to bolster the screening effort and they ordered more than half a billion testing kits from China.

But Dr R.R. Gangakhedkar, the chief of epidemiology at the Indian Council of Medical Research, said he has asked health authorities to halt the tests for antibodies because of conflicting results.

"This is a first-generation test developed in just three-and-a-half months and needs refinement," he said.

"We have advised the states not to use them for the next two days until we come out with an advisory."

The antibody tests do not always pick up early-stage infections but show whether a person had the virus in the past, even if the person had no symptoms of Covid-19.

In comparison, the swab test, known as the RT-PCR-technology swab test, shows whether a person has the virus at that moment by looking for it in nose or throat secretions.

The health minister of Rajasthan said the two tests were in some cases producing conflicting results, raising doubts about reliability.

"The kits were used for testing of patients who have already tested positive for coronavirus," Mr Raghu Sharma, said. "But the rapid test kits found them negative, which raised questions about the credibility of these kits."

Both tests are seen as critical in the coronavirus fight, but antibody tests are a relatively cheap, fast means to sort populations into risk groups and measure the spread of the virus.

India has detected 20,471 cases of the coronavirus, after an increase of nearly 1,000 cases in one day, according to the government data.

There have been 652 deaths, still a small number compared with tolls in many other countries, but officials say the infections could rise once a nearly six-week lockdown is lifted on May 3.

Big cities like Delhi and Mumbai and their adjoining areas have taken the brunt of the infections, leaving the countryside less affected.

India's 1.3 billion people have been ordered to remain indoors for 40 days to slow the spread of the virus.

While the number of cases of infection is still increasing, health officials said the speed of transmission is slowing, thanks to the lockdown.

The doubling rate or the number of days it takes infections to multiply by two had increased to 7.5 days, up from 3.4 days before the lockdown, Health Ministry Joint Secretary Lav Agarwal said.

"This is an extremely positive trend," he said.



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