ZURICH (REUTERS) - Swiss drugmaker Roche aims to offer blood tests to identify those who had been infected with the coronavirus by next month, potentially helping inform locked-down nations of who might have some immunity and be able to resume work or contact with the public.

The Basel-based company said on Friday (April 17) that it wants to make the antibody test available by early May in countries that accept European CE regulatory standards, and is seeking US Food and Drug Administration emergency authorisation for its use in the United States.

It plans by June to boost test production to "high double-digit millions" per month, said Mr Thomas Schinecker, Roche's diagnostics head.

Roche joins a global race in which US-based Abbott Laboratories and Becton Dickinson and Co, Italy's DiaSorin and others hope to sell tests that demonstrate people's immune systems have developed antibodies in response to the new coronavirus.

While it is not yet known for sure if those who have been infected develop immunity to the new virus as with many other illnesses, accurate antibody tests are seen as essential to help nations craft strategies to end business and travel shutdowns that have battered economies around the globe.

"This is the working assumption: If you test and find people that have developed these antibodies, then at least for a certain period of time, they will have gained immunity," Mr Schinecker told Reuters. "We worked day and night on this, over weekends, to make sure we can help as many patients as possible."

Roche's test, which differs from the polymerase chain reaction (PCR) assays it also makes that use a nose swab to identify active infections, will run on more than 40,000 of its cobas e testing machines installed worldwide.

Roche's new test will identify immunoglobulin M (IgM) and immunoglobulin G (IgG) antibodies. The body quickly produces IgM antibodies for the initial fight against infection. IgG antibodies remain longer in the body, suggesting possible immunity.

Countries have various plans to use such tests to better understand the Covid-19 illness caused by the virus, and identify those who were infected but showed only mild symptoms, or none at all.

Finland, Germany, Britain and other countries have antibody testing plans. The US Centres for Disease Control and Prevention plans to use them to study community-wide transmission.

In Roche's home country, Switzerland, officials are examining tests, but warn that excitement may be premature, given positive tests may say little about actual immunity.

"What you can't say, and that's this idea that's going around, is that if I have the antibodies, then I know if I'm immune or not," said Mr Patrick Mathys, the Swiss health ministry's crisis management head. "That will take more research."

Even tests with high accuracy have weaknesses, potentially producing many false negative and false positive results. False positives could lead someone to believe they have immunity when in fact they had not been infected.

Roche's tests have met the company's own accuracy expectations, Mr Schinecker said, though it is not yet releasing final figures.

"We put our best scientists on this," he said. "What we see is that the way we've designed the assay, it's extremely specific."