ZURICH/BERLIN • Countries straining to contain a second wave of Covid-19 are turning to faster, cheaper but less accurate tests to avoid the delays and shortages that have plagued efforts to diagnose and trace those infected quickly.

Germany, where cases jumped by 4,122 on Tuesday to 329,453 in total, has secured nine million so-called antigen tests per month that can deliver a result in minutes and cost about €5 (S$8) each. That would, in theory, cover more than 10 per cent of the population.

The United States and Canada are also buying millions of tests, as is Italy, whose recent tender for five million tests attracted offers from 35 companies.

Germany's Robert Koch Institute now recommends antigen tests to complement existing molecular polymerase chain reaction (PCR) tests, which have become the standard for assessing active infections but which have also suffered shortages as the pandemic overwhelmed laboratories and outstripped manufacturers' production capacity.

PCR tests detect genetic material in the virus while antigen tests detect proteins on the virus' surface, though both are meant to pick up active infections.

Another type of test, for antibodies that the body produces in response to an infection, can help tell if somebody has had Covid-19 in the past. Like PCR tests, antigen tests require an uncomfortable nasal swab. They can also produce more "false negatives", prompting some experts to recommend that they only be used in a pinch.

Still, the alarming rise in new virus infections globally has health officials desperately pursuing more options as the winter influenza season looms.

The World Health Organisation reported more than two million new cases last week, bringing the total worldwide to 37 million, with more than one million deaths from Covid-19.

"These point-of-care tests could make a big difference," said Dr Gerard Krause, director of the epidemiology department at Germany's Helmholtz Centre for Infection Research. Dr Krause said low-priority patients - those without symptoms - could initially be screened with antigen tests, leaving the more accurate PCR tests for those showing signs of the disease.

NO TEST, NO FLIGHT

Antigen tests have already gained traction in the travel industry. Italian airline Alitalia is offering Rome-Milan flights exclusively for passengers with negative tests and Germany's Lufthansa has announced similar testing plans.

But the pandemic's vast scale has strained the ability of countries to test all of their citizens, making it difficult to track the twisting paths of infection comprehensively and prevent a resurgence.

In the US, for example, reliance on automated PCR machinery over the summer left many patients frustrated as they waited for a week or more for results.

Testing in Europe has also suffered glitches.

France carries out more than a million tests a week but its free-for-all testing policy has led to long queues and delays in results, prompting French researchers to come up with a test that they say can produce results in 40 minutes, without using a swab.

Italy does between 800,000 and 840,000 tests a week, more than double April's levels, according to the Ministry of Health.

But a government adviser, University of Padua microbiology professor Andrea Crisanti, said the country needs two million tests a week to really get on top of the virus.

In the Netherlands, where infection rates are among Europe's highest, the government has been scrambling to expand weekly testing and lab capacity to 385,000 by next week from 280,000 now. The target is nearly half a million tests a week by December.

'GOLD STANDARD'

The various testing hitches highlight a conundrum for governments: how to get people back to work while tracing the virus within the population quickly - all without running out of supplies.

Swiss diagnostics maker Roche announced plans on Tuesday to launch a new antigen test by year end that can be processed on lab machines at up to 300 tests per hour, not counting collection time.

Its rivals, including Siemens Healthineers, Abbott Laboratories and Becton Dickinson, also offer numerous Covid-19 diagnostic tests.

Roche said its test could be used in places like nursing homes or hospitals, where fast results could prevent a potentially lethal outbreak.

Expert opinion on just how to use antigen tests is evolving and remains the subject of debate.

Switzerland, where new cases have spiked to about 1,500 a day from as low as three in June after schools reopened, is only now validating the accuracy of the rapid tests. "Deployment of the rapid tests - where it makes sense - will be integrated into our testing strategy," a spokesman for the Swiss federal health ministry said.

In Germany, Dr Sandra Ciesek of University Clinic in Frankfurt said rapid antigen tests could be an option for asymptomatic patients planning to visit elderly patients at nursing homes.

But people should refrain from using them as a definitive substitute to judge their infection status.

"The PCR test remains the gold standard," Dr Ciesek said. "An antigen test should only be used as an alternative if PCR is not possible in a timely manner."

REUTERS