Jan. 28, 2021 -- China is not giving up on nasal or throat testing, but the country has adopted a new method for detecting the coronavirus: anal swabs.

Anal testing is being used so far only on select groups, mainly high-risk cases and people in quarantine. Some people who have been subjected to anal testing include passengers arriving in Beijing and a group of more than 1,000 schoolchildren and teachers who were thought to have been exposed to the virus, Forbes reported.

The use of anal swabs is limited because it’s invasive and inconvenient. If a stool sample cannot be obtained, a saline-soaked cotton swab about 1-2 inches long is inserted into the anus, with the sample tested for active traces of the virus.

Li Tongzeng, deputy director of the respiratory and infectious diseases department at Beijing Youan Hospital, said in an interview with state media that anal swabs appear to be more accurate at detecting the coronavirus than nasal or throat testing.

The virus lives longer in excrement or the anus than in the respiratory tract, he said, meaning anal testing might have fewer false negatives.

Last summer, Future Medicine published research by Chinese scientists into a small number of COVID patients. In a few cases, people tested negative for COVID in throat and spit testing but tested positive with anal swabs.

“We propose anal swabs as the potentially optimal specimen for SARS-CoV-2 detection for evaluation of hospital discharge of COVID-19 patients,” the scientists wrote.

But not every scientist supports the practice of using anal swabs.

Yang Zhanqiu, a pathologist at Wuhan University, told the Global Times that nasal and throat swabs are still the most efficient tests because the coronavirus is contracted through the respiratory system, not the digestive system.

"There have been cases concerning the coronavirus testing positive in a patient's excrement, but no evidence has suggested it had been transmitted through one's digestive system," he said.

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Sources

Forbes. China Deploys Anal Swab Tests To Detect High-Risk Covid-19 Cases
People’s Daily. “Expert interpretation - Why does nucleic acid testing increase with anal swab sampling?”
Global Times. Beijing tests for COVID-19 using anal swabs, where virus may survive longer: experts

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