Governments and companies are relying on these tests to measure how widely the virus has spread as they rush to get their economies and employees back to work and avoid a second wave of infections, even if they do not prove immunity
The market for Covid-19 antibody tests is red-hot. It has ballooned in a matter of months as hundreds of products flood the world for people who want to find out whether they've already had the virus.
The problem is, some of them don't work properly.
As a result, European authorities aim to tighten regulation of the new sector, to weed out tests that give consistently inaccurate results and crack down on companies that make false claims, three sources familiar with the plans told Reuters.
Much is on the line, even beyond the potential for fraud.
Governments and companies are relying on these tests to measure how widely the virus has spread as they rush to get their economies and employees back to work and avoid a second wave of infections, even if they do not prove immunity.
False results could undermine that effort.
Many people have also been using kits, also known as serological or blood tests, at home or for personal checks in clinics.
Since April the number of antibody kits carrying the region's CE mark of quality doubled to more than 200, according to a list compiled by the EU Commission, the EU executive.
Some of these kits are unreliable, half a dozen national regulators and industry sources across Europe told Reuters. A dozen tests have been subject to regulators' warnings for mis-selling, including in Spain and Sweden.
At least nine of them are no longer allowed to be sold in the United States, according to a Reuters analysis of public data from the Food and Drug Administration, which clamped down on the sector last month.
The EU Commission is now looking at changing the self-certification regime that allows test-makers to label their products with the CE mark themselves, an EU official and two European regulatory sources told Reuters, declining to be named as the plans have not been made public.
Among changes being examined, companies could be required to have tests reviewed by independent watchdogs before placing the CE mark on them, the sources said.
That would mark a significant toughening of the current regime, whereby makers merely self-certify compliance with EU safety rules and supervisors can subsequently penalise them if their claims turn out to be false.
Guidance setting out minimum performance criteria for tests could also be adopted, the two regulatory sources told Reuters. Under current rules, kits can carry a CE mark regardless of their accuracy.
When asked about the plans, a spokesman for the Commission, the EU executive, said it was "currently considering the best way forward".
"We are assessing a number of different instruments available together with member states to see which action is the most appropriate," he added.
'SPENDING LOTS OF MONEY'
Scientists have not yet definitively proven whether or how long Covid-19 survivors are immune to new infections, even if they developed antibodies.
Nevertheless, many people are willing to pay for the tests - and many don't come cheap, selling for anything from a few euros to more than 150 euros in some private clinics in Europe.
It's a potentially lucrative business: testing about 450 million people in the EU would cost billions of euros based on such prices.
"People might be spending lots of money for nothing," said Pauline Constant of BEUC, a European consumer organisation.
Severin Schwan, CEO of Swiss drug giant Roche which has its own antibody test, sounded an alarm in late April, when he said some tests on the market were a "disaster". The World Health Organization also warned that tests on the market were not sufficiently reliable and could not prove immunity.
Such comments were backed up by a study conducted by the Dutch regulator who found in May that none of 16 reviewed tests were trustworthy.
"The test results are not reliable. The percentage of false positive and false negative results is too high," the study concluded, without naming the manufacturers.
"Those tests are quite meaningless," said a spokesman for the Dutch Health and Youth Care Inspectorate, a part of the health ministry that supervises public health.
Despite the poor results, clinics and labs in the Netherlands are still allowed to offer these tests.
INDUSTRY BACKS RULE REVIEW
Introducing an independent review of products would bring forward an EU reform that had been agreed before the coronavirus crisis but was not due to take effect until 2022.
In the absence of an EU performance standard for tests, France has already set its own thresholds. About 60 kits have met the country's requirement of at least 90 percent of correct positive results, a measure known as sensitivity, and 98 percent of correct negative results, so-called specificity.
Under current EU rules, overseen and enforced by national watchdogs, manufacturers must seek authorisation before using the CE mark only for so-called home or self-tests, which are those who can be performed at home without professional advice.
About a dozen antibody devices have been unlawfully marketed as CE-marked self-tests without prior authorisation, according to the Spanish and Swedish regulators.
Low performance is not in itself illegal and has been tolerated in Europe in the initial phase of the Covid-19 crisis because tests were rare. But companies cannot exaggerate the accuracy of their devices.
An official at the Swedish regulator said the body had yet to start performance checks, while two pharmaceutical industry sources said such checks were rare in Europe.
There is however a balance to be struck on regulation, according to industry experts who worry that if new rules are too strict or onerous they could delay the deployment of tests to conduct large-scale epidemiological surveys.
But greater scrutiny could help improve the tarnished reputation of the sector.
MedTechEurope, the trading body for medical technology firms including Abbott, Roche and Siemens Healthineers, backed plans to review industry regulations.
"We support the intention of these plans, and would welcome the opportunity to provide the industry's input into this debate on how to best ensure only well-performing tests are on the market," it said.