There has been a surge in demand for self-testing kits as Covid-19 cases rise across the nation.
The spread of the third Covid wave has been faster than that of the second one, according to some experts. Reluctance to follow Covid-safety protocols is adding to the number of cases.
India logged 2,47,417 new coronavirus infections on Thursday, the highest in 236 days, taking the total tally of Covid cases to 3,63,17,927, including 5,488 cases of the Omicron variant.
As the nation is heading towards a Covid peak, the Delta and Omicron variants are causes of heightened concerns.
The sudden surge of Covid cases has increased the demand for self-testing kits across the nation.
Priced between Rs 250 and Rs 350, these kits are a cheaper alternative to the forever-fluctuating rates of RT-PCR (Reverse Transcription–Polymerase Chain Reaction) tests that are conducted by health technicians.
More than the price, these at-home Rapid Antigen Test (RAT) kits offer a sense of freedom and flexibility to the home-bound crowd. But there’s always a catch that comes with ease.
ICMR-approved at-home Covid test kits
How reliable are home-testing kits?
Most rapid antigen tests are conducted using nose swabs, and the results are out in just 15 minutes.
While home-testing RAT kits are extremely convenient to use, Dr Vikas Maurya, HOD and Director-Pulmonology at Fortis Hospital, Shalimar Bagh, says they are less reliable than gene testing, and can give a false-negative or even a false-positive result.
Explaining the false-positive result, he says it is extremely uncommon, but one in 100 or more tests may show this result due to the detection of certain proteins.
Adding to the discussion, SRL Diagnostics CEO Anand K says RATs can give a false sense of security to patients when it gives false-negative results. “Home kits are only advisable if people are using it for precautionary testing,” he adds.
Dr Laxman Jessani, Consultant-Infectious Diseases at Apollo Hospitals, Navi Mumbai, says self-test shows a false-negative result in 25-30 per cent of the cases. “A negative result means the test did not detect the virus or you may not have contracted it, but it does not rule out the infection,” he explains.
RATs are seen as efficient, but their accuracy is still debatable, says Dr Naganath Narsimhan Prem, Consultant-Department of Geriatric Medicine, Jaslok Hospital. “Covid self-tests are a bit behind in accuracy as the chances of a false-negative is much higher than in RT-PCR,” he says.
Maintaining strict hygiene while performing the test is mandatory, else the sample may get contaminated.
What makes RT-PCR the ‘gold standard’ for Covid testing?
RT-PCR test studies the ribonucleic acid (RNA) genome in the sample and detects the genetic component of the virus to present a more accurate result.
Dr Vasunethra Kasargod, Consultant Pulmonologist and Chest Physician at Manipal Hospitals Millers Road, Bengaluru, says RT-PCR (molecular testing) is considered the “gold standard” in Covid testing as it can diagnose the infection in asymptomatic individuals as well.
While an RT-PCR test cannot give any information on the kind of variant that may have caused the infection, it has been able to accurately detect the virus caused by any variant, including Omicron. “The only method to find the variant responsible for the infection would be genome sequencing,” Anand says.
Dr Jessani says there is only one Indian Council of Medical Research-approved RT-PCR 3 gene test that can detect the Omicron variant. “The Tata MD Check Omisure test works by detecting simultaneous S-Gene Target Failure (SGTF) and S-Gene Mutation Amplification (SGMA) which points to infection by Omicron,” he says.
RAT or RT-PCR: How do you decide?
Rapid tests are approximately 60 per cent accurate in patients without symptoms and around 70 per cent with symptoms. However, the RT-PCR accuracy is more than 90 per cent when correctly done and the patient is symptomatic.
Make sure you let the swab sit for the required time in the testing solution and on the testing card. Do not meddle with it.While RT-PCR allows detection of the SARS-CoV-2 genetic material present in nasopharyngeal fluid samples taken through throat and nasal swabs, RAT is capable of detecting certain molecules found on the surface of the virus.
“Nasal swabs are more accurate than oral swabs,” Dr Maurya points out.
RAT requires more virus in the sample to report a positive result. “Rapid tests have a high risk of false-negative results — that is, showing a negative result when you actually have Covid,” says Dr Jessani.
If the test is negative and the patient has typical Covid-symptoms of fever, severe sore throat, body ache and cough, then Dr Kasargod recommends a RT-PCR test. However, she says that one need not take a repeat RT-PCR test if the RAT test is positive.
Why do RT-PCR tests cost more than RATs?
RT-PCR, a specialised molecular test, amplifies the genetic material, making it more sensitive. “The RT-PCR test is more sensitive when it comes to gene testing and, hence, more accurate,” says Dr Maurya.
When conducting RT-PCR, the SRL Labs boss explains that the test requires special kits, equipment and a highly-skilled technologist to perform the test. “These add up to the cost.” It costs Rs 1,200 in 2020 and Rs 800 in early-2021. The government capped the price of the RT-PCR test at Rs 500 in October 2021, according to a report in The Times of India.
An RT-PCR currently costs Rs 500 to Rs 1,200 — depending on the state and whether or not the sample is collected at home. The cost of getting the rapid RT-PCR test done at airports is a lot more expensive — Rs 3,000 or more, in some cases.
Factors to keep in mind when self-testing
How to effectively use the self-testing kit?
Taking one’s own sample can be a challenge. The fear of pain and discomfort makes the process difficult.
One has to be extremely careful during the collection of samples and testing as both the stages are important. Also, maintaining strict hygiene while performing the test is mandatory, else the sample may get contaminated.
Since antigen tests have lower sensitivity, it is advisable to strictly follow the instructions that come with the kit. Not doing so may affect the test’s reliability. Make sure you let the swab sit for the required time in the testing solution and on the testing card. Do not meddle with it.
Any line appearing on the Covid-testing card after the given time may not be accurate. Faint lines on the Covid-testing card can also be confusing, and warrants an RT-PCR for more accurate testing.
It might be prudent to keep an RAT test kit at home. But follow it up with an RT-PCR test also. Always seek a doctor’s advice. Remember, they are the experts.
Steps to follow when using self-testing kits