This week the World Health Organization (WHO) will come up with a new guideline for the use of rapid tests. These coronavirus tests should relieve the laboratories and the GGDs. Worldwide, major pharmacists are bringing several rapid tests on the market. They are not a solution for everything, says virologist Chantal Reusken. “But they can take the pressure off testing. They are very useful for that.”
Reusken, virologist at RIVM and involved in, among other things, testing policy, test capacity and test innovation, contributes to the WHO guideline. “The message will be, inter alia, that rapid tests need to be extended, validated in the intended context for use”
She means that the tests can help if, for example, there’s an outbreak in a nursing home and it needs to be clear quickly whether it’s corona. “See how widespread the infections are. But after that you have to do the regular PCR tests for final confirmation.”
She calls it a two-step system. “This actually applies to all situations in clearly identified settings where an outbreak is suspected. Then you can already take an initial quick action to prevent further infections pending the final results with reliable tests,” Reusken says.
Virologist Marion Koopmans also says that the rapid test can be a good addition to the current PCR test. “But there is still a lot of uncertainty about the reliability of the tests. There are currently about 800 different rapid tests offered to the WHO. They are currently separating the wheat from the chaff. Every producer is very positive about the operation of the tests, but there is plenty of reason to take a critical look at them”
According to the virologist, it is very important to know under what conditions tests work well. “Do they also work well in people without complaints?” The OMT will soon issue advice on the use of rapid tests and hopes to be able to say something about this. OMT member Koopmans does not yet want to anticipate this advice.
According to Reusken, rapid tests can also be useful in situations where PCR testing is not available. “For example, in rural areas of Africa. Pending final results that can then take days, you can then, for example, start infection prevention and control measures on the basis of such an antigen test”
Koopmans: “With the rapid test you could say: high-positive testing has priority over source and contact testing. This would enable you to do source and contact research more quickly.”
The reliability of the rapid tests remains a problem for the time being, says Reusken. The sensitivity is usually very low and often doesn’t exceed 50 percent. Some manufacturers – such as Roche – claim a sensitivity of 96 per cent, but according to Reusken that still needs to be investigated independently first.
“Manufacturers often test mainly among seriously ill people with clear symptoms. That will benefit the sensitivity percentages”, says Reusken. “It’s interesting to know whether the test also works in people who have no symptoms or very mild symptoms. What the WHO is likely to do is indicate a lower limit of sensitivity of rapid tests for use in specific situations, for example 70 to 80 percent”
Various laboratories in the Netherlands are asked weekly for their results. Reusken: “The PCR tests are the gold standard. In the test designs in which the value of the rapid tests is now being investigated, the rapid tests are carried out alongside the PCR tests” This is only done with the consent of the person being tested.
The rapid tests will not be available in the Netherlands until they meet all the requirements. Reusken: “And there must be a robust delivery. Most importantly, they must first prove that they are sufficiently accurate”