Is preventive testing of employees for Coronavirus beneficial?
The demand for preventive testing of employees is understandable. There are a number of factors to explain why mass testing in the workplace has not been an obvious approach until now. But it would be amiss to throw the baby out with the bathwater. A proper plan for testing may be an important addition to contact tracing and faster detection of infected employees.
There are various Coronavirus tests available at the moment. Some detect the virus itself, others look for the presence of antibodies in the blood. The renowned nose or throat swabs for detecting SARS-CoV-2 are most commonly used. These PCR tests have one disadvantage: a sensitivity of just over 70%. This means that out of ten infected people, three people incorrectly show a negative test result. Positive results are conclusive, however.
Antigen tests deliver results within minutes, but only have a reliability of 60%. For this reason, these tests are solely used as a de facto first screening test. A different test is used to confirm the result.
In addition, we have the antibody tests that check the immune response to Covid-19. It takes two or three weeks for sufficient antibodies to be detectable in the blood. This test can be used to determine whether someone has come into contact with the virus.
No scientific basis
Are these tests now ready to be used in the workplace? “The antibody tests are not, for various reasons”, says Dr. Gretel Schrijvers, General Director of Mensura. “We don’t (yet) know whether antibodies protect a person against a new infection and how long this possible protection might be effective. It is also unclear whether it is possible you won’t get sick again, but are still contagious if you’re infected a second time. What’s more, the occupational doctor is bound to professional confidentiality which prevents him from sharing the result with the employer.”
What about the PCR tests? Dr. Gretel Schrijvers: "In the present circumstances and with the knowledge we have right now, I am convinced that they are useful, provided they are used wisely. The higher the probability of the presence of disease in the test group, the higher the predictive value of the test result. As such, it is not beneficial to test your entire workforce. Besides, it's a snapshot: being virus-free doesn't necessarily mean you're virus-free a few days later. In this respect, repetitive testing may be required.
Specifically, this means that for the majority of companies it only makes sense to test high-risk contacts, which may be a relevant extension of contact tracing by the government (which can then further map out the private contacts section).
A detailed picture of high-risk contacts
So, the key is to determine the high-risk contacts within each company. "That's why Mensura developed a risk analysis that does just that," Gretel Writers explains. “After all, there are roles or circumstances that make it difficult or not possible to comply with the prevention measures we are all so familiar with by now. This risk analysis provides companies with a clear picture of who is at increased risk. It allows for quick action and testing if a colleague happens to show symptoms, or an employee receives a phone call from the contact tracing team, and therefore significantly increases detection capabilities. Until there are more conclusive tests, or an effective vaccine, this seems to be the most beneficial way of testing.”
Recognition of occupational disease and specific settings
Furthermore, occupational doctors are currently also using diagnostic tests in specific situations, such as requests for recognition as an occupational disease and for certain maritime and offshore activities.
Covid-19 has been recognised as an occupational disease for those working in healthcare or other hospital services, care institutions, residential care centres, rest homes and collective housing for sick or disabled people where an outbreak of Covid-19 has occurred. Those who do not work in the health sector may be recognised through the 'open system'. These workers must be exposed to the occupational risk of the illness, have experienced the illness, and be able to prove that they have contracted the illness as a result of their work.
A specific group of workers can also be tested in specific circumstances, such as in maritime shipping or for offshore activities, in order to rule out asymptomatic infection. This avoids importing contamination within an isolated group to environments where medical assistance is not always available (e.g. oil rigs).