The success story of Bündner company and school tests is coming to an abrupt end for now: The Omicron wave triggered an avalanche of tests that the laboratory was no longer able to cope with. “pooling,” one of the success factors of the test strategy, was her undoing.
As recently as December, the Risch laboratory in Buchs (SG), which is responsible for the Bündner operational and school tests, doubled its capacity for corona tests. As a result, you could assume that you were well prepared for winter: The waiting time between the test and delivery of the result should be one to one and a half days. Infected people could thus be quickly “withdrawn from circulation” and chains of infection interrupted.
The regular tests in Graubünden companies and schools were very well received: In December, a total of around 60,000 people took part.
In order to be able to handle such a volume at all, the saliva samples are tested in pools (groups). In the case of school classes, the samples of 8 to 10 people are mixed together directly at school. In the laboratory, only one PCR analysis must then be carried out per pool. Only when a pool contains a positive person are all students in this pool individually retested. Students must stay at home until the result is available.
Pooling is also used in operational tests. Here, however, the pools are only created in the laboratory, where five saliva samples are combined to form a pool. If a pool is positive, the individual tubes of this pool can be checked directly in the laboratory. It is not necessary to re-test the test subjects. Only employees who test positive must stay at home.
And then came Omicron...
The advantage of pools is obvious: As long as only a few of the pools are positive, the number of PCR analyses carried out can be significantly reduced. In December, only every 10th company pool and every 15th class pool was positive. Just in time for the winter season, however, a variant of the virus appeared with Omicron that is four to six times more contagious than the previous variants. Omikron and the beginning of winter season led to a marked increase in interest in operational tests.
At the same time, the proportion of positive pools from companies tripled, and the positive pools from schools also increased by a third. The sharp increase in infections from Omicron increased the total number of positive tests by 62 percent and also significantly exceeded the previously doubled laboratory capacity. The result: Once again, it often took two or more days for the test subjects to receive the results.
However, because Omicron is not only more contagious than Delta, but also less time elapses from infection to spread, results that only arrive after such a long period of time are no longer worth much. The tests only make a limited contribution to preventing the spread of the disease.
Hopefully temporarily
The government therefore had no choice but to suspend operational and school tests for the time being. The decision is annoying, but laboratory capacity is now available again for the tests that have the most impact on the spread of Omicron: people with symptoms, employees in the health and care sector, and the youngest students in primary school and kindergarten, almost all of whom are still unvaccinated.
The suspension of company and school tests in Grisons is hopefully only temporary: On January 24, the government wants to decide whether they can be resumed in any way. Until then, it is important to pay particular attention to the remaining protective measures in order to flatten out the Omicron wave as much as possible.
Christian Gartmann is the initiator and project manager of the “Corona II Engadin” task force.