Users on social media have been sharing news that China is using Anal Swabs for detecting Coronavirus infections. While this is true, it seems that this will not be applied to everyone being tested.
These anal swabs are soaked in saline, and inserted into the anus and rotated.
If you see this France24 article, you will notice this part:
But the anal swabs method "can increase the detection rate of infected people" as traces of the virus linger longer in the anus than in the respiratory tract, Li Tongzeng, a senior doctor from Beijing's You'an Hospital, told CCTV.
As well as:
CCTV said on Sunday anal swabs would not be used as widely as other methods, as the technique was "not convenient."
Then in this Washington Post article you see this quote:
Some Chinese doctors say the science is there. Recovering patients, they say, have continued to test positive through samples from the lower digestive tract days after nasal and throat swabs came back negative.
So this additional test seems to be limited to those who have tested positive, to make sure that the virus is completely cleared from their body, and it is not being shed in the upper respiratory tract, or in the digestive tract.