- China is using an anal swab test for COVID-19, in “key groups”, because it’s supposed to be more accurate.
- An anal swab test involves inserting a small cotton-tipped swab into the rectum.
- Anal swabs “are not legal”, but tests it makes sense, said professor of microbiology Joanne Santini.
- Visit the Business Insider home page for more stories.
China has introduced anal swabs as a new type of test that can detect coronavirus more accurately.
“If we add the anal test, it can increase our rate of identifying infected patients,” Li Tongzeng, an infectious disease specialist at Beijing You’an Hospital, told China Central Television on Sunday.
“But of course, considering that collecting anal smears is not as convenient as throat swabs, at the moment only important groups, such as those in quarantine, receive both,” added Tongzeng.
An anal swab test means inserting a 3-5 cm (1-2 inch) cotton swab into the rectum, which is then sent to a laboratory for testing for the virus. They are analyzed in the same way as the Polymerase Chain Reaction (PCR) coronavirus tests done on the nose or throat.
Tonzeng said a study showed that the virus lasts longer in the anus or stool than in the respiratory tract. Therefore, an anal smear or fecal sample can be useful to identify the disease in mild or asymptomatic cases.
But Yang Zhanqiu, deputy director of the pathogen biology department at Wuhan University, told the state tabloid The Global Times that since the virus has been proven to be contracted by the upper respiratory tract rather than the digestive system, the most effective are still nasal and throat swabs.
“There have been cases related to positive coronavirus testing in a patient’s droppings, but no evidence suggests that it was transmitted through the digestive system,” said Yang.
Joanne Santini, professor of microbiology at University College London, told Insider that anal swabs are not a good way to test, but they make sense. “It’s the most obvious thing to do,” said Santini.
Santini explained that the virus binds to the human body using a receptor called ACE2, and there are many ACE2 receptors in the intestine. Viral load – the amount of virus released – can also be higher in the stool, especially if someone suffers from gastrointestinal problems caused by the coronavirus. And the elimination of the virus can last longer in the feces than in the sputum.
“Even though a common form of infection is through breathing, I think there must be some infection going through the intestine and the mouth,” she said. “There is evidence that SARS-CoV-2 in feces is infectious, as are other viruses, such as norovirus and other coronaviruses.”
Santini said that poop samples, however, would be preferable to anal smears because they are less invasive and can be particularly useful for collecting samples from children.
“It is less painful for children, and people do it all the time for other tests,” she said. “You don’t have to go anywhere and you can do it yourself.”