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 infections jumped by 4,122 yesterday to 329,453 total, has secured nine million so-called antigen tests per month that can deliver a result in minutes and cost about $5.90 each. That would, in theory, cover more than 10 per cent of the population.
The US and Canada are also buying millions of tests, as is Italy, whose recent tender for 5m tests attracted offers from 35 companies.
Germany’s Robert Koch Institute (RKI) now recommends antigen tests to complement existing molecular 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’s surface, though both are meant to pick up active infections. Another type of test, for antibodies 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 they only be used in a pinch.
Still, the alarming rise in new infections globally has health officials desperately pursuing more options as the winter influenza season looms.
The World Health Organisation reported more than 2m new cases last week, bringing the total worldwide to 37m, with more than 1m deaths.
“These point-of-care tests could make a big difference,” said Gerard Krause, epidemiology department director at Germany’s Helmholtz Centre for Infection Research.
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.
Antigen tests have already gained traction in the travel industry. Italian airline Alitalia offers Rome-Milan flights exclusively for passengers with negative tests and Germany’s Lufthansa has announced similar testing plans.
But 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 does 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 they say can produce results in 40 minutes, without using a swab.