Thai researchers develop world’s first Covid-19 sweat test

Created by Chulalongkorn University, the quick and easy-to-use portable test device detects scents in sweat that signal infection. Each sample takes only 15 minutes to collect and provides results in 30 seconds, said a Chula press release. The sweat test is already being used in community screening, it added.

The new test is based on the success of the "Covid-19 Sniffer Dogs" project, a collaboration between Chula and Chevron. The university said the “Portable Sweat Test for Covid-19 Detection" would supplement the army of sniffer dogs in accelerating and expanding community screening.
“We took [Covid-positive] samples that the dogs found and searched for specific substances they could detect," said Asst Professor Chadin Kulsing, from Chula’s Chemistry Department, where the test was developed. 

"From the samples, we found that people infected with Covid-19 secrete very distinct chemicals. So we used this finding to develop a device to detect the specific odours produced by certain bacteria in the sweat of Covid-19 patients.” 
Chadin added that this was the first time Covid-19 has been detected via these chemicals.

How does body odour prove viral infection?
Human sweat can have more than 100 unique odours, from deodorants and bacteria that feed on sweat and other skin secretions.
"In people infected with Covid-19, the bacteria react to the virus and produce distinct odours unique to Covid-19 infection,” Chadin explained.

To develop the portable sweat test device, he took a commercially available portable toxic-chemical analyser and fitted it with a filter to detect the virus.
The test kit consists of a cotton swab and a glass vial.
The cotton swab is placed in the armpit for about 15 minutes, then placed in the glass vile which is sterilised with UV rays.  

“The technician then draws an appropriate amount of the sample using a suction hose, and pressurises it in the analyser to check the results,” explained Chadin.
The advantage of this method is that it can be adapted to detect variants of the virus through their unique sweat signatures.

“The equipment should be able to handle the variable chemicals with just a change of filter,” Chadin added.
In field tests on 2,000 people, the sweat test performed on par with the PCR (Polymerase Chain Reaction) test with 95 per cent sensitivity and 98 per cent specificity. 

However, Chadin advises that people who test positive in the sweat test should get a PCR test for confirmation.
The portable sweat test device is still in the research and development phase, with Chula and the Department of Disease Control collaborating on field tests in communities. Chadin said the test was being used for proactive screening in communities with emerging clusters. 

“We are also working with Sniffer Dogs Mobile Units to take over from the canines during their rest period,” he added.