SMS with a fake positive result
“A friend of a friend went to get tested with her daughter. They registered, but because there were too many people, they left after three hours and went home. A few days later, they both received an SMS, telling them they are positive.”
This hoax has been appearing since spring of 2020 in different versions across the whole world. There are allegedly tens of people who know someone who went through something similar. None of the people who this allegedly happened to have ever been able to show any proof like an SMS with the test number or the name of a laboratory. If you ask them for proof, they usually retract their claim about a “positive test”.
This story is not plausible from a logical standpoint for a number of reasons: If you have an electrical request form, you don't have to wait for your test for hours, the waiting time is usually max 1 hour. The registration, explanation of the process and assignment of a specific person to a specific test happens right before the test (after having waited in the queue). Until that point, you are only registered in the system of online request forms because no one can tell which testing site you will choose to visit. The only option for a false SMS to be sent is if the wrong personal identification number or the wrong phone number were entered. This, however, is not an error in the system.
The probability of a false PCR test result
“This hoax also comes from a video from lawyer Reiner Fuellmich, where he claims that “the possibility of receiving a false positive test is between 89-94%, so almost certain.”
According to a study by Oxford university the accuracy of PCR tests is between 95-99%. Other studies prove the same thing. The results of many other available PCR test studies show that don´t react to any other viruses, including other coronaviruses.
An explanation of the whole hoax (in Czech).
Oxford university study.
Automatic positive test
“If you don't arrive at a test after having been in contact with someone who is Covid-19 positive, you are automatically seen as positive as well.”
If you are ordered to go get tested and placed in quarantine after having met someone positive, you have two obligations. Two arrive at the test and to follow all the rules for being in quarantine. If you do not arrive at the test, you can be fined but on no account will you be seen as positive. The result can only be determined as a result of a test. If all the samples can't be done in one day, they are tested the next day. This can be seen in the number of positive tests in a day, when Mondays in general have the lowest numbers, because less tests are carried out during the weekend and so it isn't necessary to run tests from previous days.