What does the ct-value mean?
In simple terms, the cycle threshold indicates how long a sample has to be examined in the laboratory, i.e. how many cycles are required before a positive result is obtained, i.e. how many „rounds“ the sample material has to go through before the SARS-CoV-2 yield can be detected. If viral material is detectable after a short period of time, this probably indicates a high viral load and the ct value is low. If the ct value is higher, e.g. 30, this simply means that the sample had to go through many rounds until virus material was found.
At ct values above 30, the virus is more difficult to cultivate according to current knowledge, which speaks for a lower infectivity of these patients. The ct value is, however, influenced by the place of sample collection, the time of transport and the test system used, so that it can only be an indication and is not meaningful on its own.