Should you trust Covid self-test kits?

Tap water gives a positive result in a video now doing the rounds. Here is what Bengaluru doctors are saying about it

A video of a Covid self-test kit being placed under a tap and displaying a positive result has gone viral.

Metrolife asked experts about the accuracy of home-testing kits.

Some household liquids can give a positive result when poured on self-test kits, but the tests remain accurate when used as directed, say doctors.

“The self-test kits have a 70 to 90% accuracy. They come with a set of instructions for a reason. If the instructions are not followed closely, they may give false results,” says Dr Gourishankar Reddy, head of Covid ICU at a major hospital.

The Indian Council of Medical Research has currently advised symptomatic individuals to use home testing kits.

“The test is recommended only to symptomatic individuals, and those who have been in close contact with Covid positive people and high-risk individuals with pre-existing health conditions. But the panic around the third wave has caused many to take the test unnecessarily,” he says.

Meddling with the antigen self-test kits can set off the pH balance resulting in false positives, says Dr Raghu J, infectious disease specialist. The acid-base balance of a solution is known as pH balance.

“The antigen test comes with a buffer solution, which consists of a 99.7% saline solution, and this is what provides stable pH and makes the test work. If you alter this with any other liquid, it imbalances the pH levels and provides a false positive. This is what has been happening in such videos,” he explains. He believes people need to be fully aware of how the test works to avoid the spread of such misinformation.

“Once something goes viral, more and more people fall for it. Rapid antigen tests have been produced after much research and are very reliable,” says Dr Raghu.

The chances of false negatives are higher than the chances of false positives. “With an antigen test, if the result is positive then it is 100% positive, but you can’t be too sure about the negative results. Sometimes, if the viral load is too low the test might fail to pick up on it. And if a professional is not doing it, there are chances one might not take the nasal swab properly,” he says.

To ensure the tests work accurately, it is best to also have an online consultation with a doctor, say doctors.

What’s PCR and RAT?

When it comes to Covid-19, two types of tests — antigen and molecular — help identify the presence of the virus in the body. While a molecular test, also known as PCR (polymerase chain reaction) test, takes about five hours to provide results, a rapid antigen test reveals the status within 15 minutes. The home self-test kits now in use are rapid antigen tests.

Home testing: Things to keep in mind

Follow all instructions provided by the manufacturer.

Wash and sanitise your hands before and after taking the test.

Do not meddle with the swab. Avoid retesting.

Self-test kits disposal risk

The rampant use of self-test Covid-19 kits is proving to be a health hazard for pourakarmikas collecting waste from households, and also for those who segregate waste. The test kits are mixed with household waste and are not being set aside as bio-medical waste.

Last week, Hasiru Dala, a social impact organisation working with waste pickers, posted a video of Kumudha, a dry waste collection centre operator from J P Nagar, highlighting the importance of properly disposing of testing kits.

“Women working in our centres are afraid to segregate waste, and many of them have fallen sick,” she says.

She suggested that pharmacies selling self-test kits inform customers that they should discard them separately as bio-medical waste. “Although the chances are low that one is infected from disposed test kits, there is still a possibility,” says Dr Raghu.

Public health researcher Dr Prashanth N Srinivas says it is the responsibility of the citizens to properly dispose of the test kids as clear guidelines are provided for it. Covid-19 test kits are contaminated with body fluids of a potentially positive or symptomatic person and hence must be handled as ‘domestic hazardous waste’.

“According to Pollution Control Board rules, urban local bodies are responsible for ensuring the safe collection and disposal of such waste in yellow bags, which are to be discarded separately,” he says.