On New Year’s Eve, the Indian government wrote to states encouraging them to promote the use of COVID-19 home tests, especially for people who are experiencing symptoms, in a bid to avoid straining local health systems.

During last year’s delta-driven surge, an explosion in cases overwhelmed hospitals and testing labs. But last month, as new infections fueled by the omicron variant skyrocketed, so did the number of people testing themselves at home across India.

In the first 20 days of January, around 200,000 people shared their test results with India’s health agency – a 66-fold increase compared to all of 2021. The strategy apparently worked. Those testing positive with speedy, though less accurate tests were told to self-isolate at home, allowing hospital beds to remain available for the most vulnerable.

But experts say this figure is likely only a fraction of the actual number of tests used. Despite rules requiring people to share their results with authorities, many aren’t doing so. This means the country’s already patchy testing data is even less accurate and that future clusters may go undetected.

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It’s a problem some states in India are already flagging. In Maharashtra, state health official Dr. Pradeep Vyas recently appealed to all users to report their results. And since tests don’t differentiate between omicron and the deadlier delta variant, which also continues to spread in India, he warned there are still vulnerable people who need hospital care.

“Suddenly there may be stress on our health infrastructure,” he wrote in a letter to authorities last month.

Since January, pharmacists in the state have begun keeping records of those buying home tests. But this isn’t the case in most Indian cities.

“If I had to guess, maybe only 20% of people using home tests are reporting it,” said K Srinath Reddy, president of the Public Health Foundation of India, adding that every test result ideally should be reported so authorities can track the virus.

“If you’re not reporting it then your sample can’t be sent for genomic analysis, and then you may miss tracking clusters and variants,” he said.

In interviews with The Associated Press, several people in the capital New Delhi admitted they tested positive using home tests but didn’t share their results with authorities.

With the highly contagious omicron variant still spreading throughout Asia, more countries are making a difficult tradeoff between accuracy and speed, deploying the nimble home tests to make sure patients don’t flood hospitals.

In South Korea, officials said Wednesday that free coronavirus rapid test kits would be available at kindergartens, elementary schools and senior welfare centers starting next week after an unprecedented wave of omicron infections. Authorities recently began moving away from a predominantly PCR testing strategy to rapid tests, even as some experts warned the latter do not reliably detect early omicron infections. People can buy at-home tests from pharmacies and convenience stores or take the tests for free at public health offices and testing stations, where anyone with a positive result is then given a PCR test.

Indian officials are relying on a centralized database where people upload their test results using a mobile app. MyLab, the first company approved for its COVID-19 home test, is producing 500,000 tests per day. Sales have jumped tenfold compared to last quarter, said Saurabh Gupta, head of strategy at MyLab. India has approved eight home tests so far, priced between $2 and $33.

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Despite the increased use of home tests, experts say they are not as accurate as lab-run PCR tests and have a higher chance of reporting false negatives.

Parul Saxena, a housewife in New Delhi, took a home test last month that turned out negative. But when she continued to have a body ache and fever, she went in for a PCR test, which confirmed what she felt all along — that she was positive for COVID-19.

India’s health ministry did not respond to questions sent via email.

Another concern is that home tests are inherently more difficult to adjust — which needs to be done as the virus evolves. While the accuracy of both home and lab tests are affected when a virus evolves, rapid tests may not be able to detect a new variant, said Vineeta Bal, who studies immune systems at the Indian Institute of Science Education and Research.

After last year’s catastrophic delta surge and a sharp rise in omicron infections to start 2022, cases in India have now stabilized with many cities reopening restaurants, schools and workplaces. On Thursday, India recorded 30,757 new cases and 541 deaths — down from a high of over 300,000 cases last month. Experts have warned that India, like elsewhere, was likely missing cases even before the emergence of home testing.

But some say it is not necessary for all positive cases to be reported to authorities. Officials can continue to study the virus’s spread through robust random sampling, said Dr. Jacob John, who studies viruses at the Christian Medical College in Vellore, a city in southern India.

Reddy, the public health expert, questioned the importance of case counts at this stage of the pandemic in India.

“Right now, this is not going to be the biggest priority — the important thing is to make sure that if people are getting very sick, there are enough healthcare facilities,” he said.

Ashley St. John, an associate professor at the Duke-NUS Medical School in Singapore, agreed that other factors are more relevant.

“I think our concern with having very accurate data on positive case numbers has lessened as vaccination rates have increased,” she said. “We know that many vaccinated individuals can test positive even without developing symptoms or severe disease. Also, we have transitioned to accepting that the virus is endemic and cannot feasibly be tracked in every person.”