The rise of rapid tests has made diagnosis easier. But it could make Omicron data ‘dodgy in the extreme.’

Isabel Reeves took a free rapid COVID-19 test in December.Craig F. Walker/Globe Staff

If a person in Sydney tests positive for COVID using an at-home rapid test but fails to report it to authorities, they could be slapped with a $1,000 fine. Halfway around the world in Massachusetts, however, even someone eager to report a positive at-home test has no means of alerting health authorities.

In the past few months, at-home rapid tests have ballooned in popularity as quick screening tools to slow the spread of the virus. Federal and state officials have slowly begun distributing the tests at little or no cost to residents. And the general public — aware of Omicron’s sharp rise, but uninterested in further lockdowns — gobbled them up, stalking pharmacies before dawn and scouring online inventory.

But even with thousands of COVID-19 infections being officially reported every day in Massachusetts, that data likely underestimates the prevalence of the virus, as countless positive rapid tests go unreported, quietly discarded into bathroom wastebaskets.

“There are certainly large numbers of people who tested positive over the last few weeks by rapid test and never sought a PCR test or were not feeling like standing in line in the cold,” said Bill Hanage, a professor of epidemiology at Harvard. “So yes, the exact numbers over the Omicron wave are dodgy in the extreme.”

The issue is not unique to Massachusetts. Only a handful of states enable citizens to submit results from their at-home rapid tests and include them in official case counts. There is no way for at-home test results to be submitted to the Centers for Disease Control and Prevention or any federal officials.

This dissonance has frustrated epidemiologists, who have emphasized the need for accurate data in order to predict surges, adjust staffing at hospitals, and monitor the long-term trajectory of COVID.

“As we edge closer to living with and surveiling this virus, it’s all the more important to have a handle on case counts,” said Mara Aspinall, a diagnostics and health care expert.

In early January, Ezekiel Emanuel, a medical ethicist and University of Pennsylvania professor, rallied five public health experts who served with him on President Biden’s now-defunct COVID-19 advisory board. In three impassioned op-eds in the Journal of the American Medical Association, the group laid out a national strategy that would allow the country to live with the virus without being caught flat-footed should a new variant or pathogen arise. Testing, much of it done at home, was a major focus.

“The US should not be reliant on extrapolating cases and outcomes from data collected from a few, underrepresentative sites. . . . The reporting system should accommodate the ability to incorporate data from at-home tests, ensuring a simple mechanism to self-report results, and should provide real-time reporting on a public website,” wrote the authors in one op-ed.

Three weeks later, the advice seems to have gone largely unheeded. Some states, including Vermont and Colorado, as well as Washington, D.C., offer online forms for people to self-report positive results. But even those portals are ad-hoc and not well publicized.

“There’s no one at the federal or state level taking control of the testing situation properly,” Emmanuel said in an interview. “So we’re going to be flying even more blind than we were before. We won’t know an accurate case fatality rate. We won’t know who or how many are getting breakthrough infections. We won’t know when surges are coming until it’s too late for hospitals to prepare. All important pieces of data that will be missed.”

Before Omicron, rapid tests were hardly a precious commodity, available in towering stacks behind pharmacy counters. It wasn’t until the highly transmissible variant blew through vaccine defenses this winter that many public health officials and the public appreciated how useful at-home tests could be.

The Food and Drug Administration — which had previously authorized rapid tests at a plodding pace — announced it would fast-track review of new tests. Seven of the 13 at-home rapid tests available in the country were authorized in the last four months. Manufacturers have struggled to meet demand, all while reaping staggering revenue.

Abbott Laboratories, maker of the navy blue BinaxNow test, notched $1.9 billion in sales related to COVID-19 testing during its third quarter, up 48 percent from the same period a year ago. The BinaxNow test alone was responsible for $1.6 billion in sales.

Quidel, which makes the white and purple QuickVue test sold at pharmacy chains and other retailers, reported revenue of $406 million from its COVID-19 tests in the third quarter of 2021.

Gopuff, a consumer goods delivery company, said sales of rapid tests have climbed 10,000 percent since the start of the surge in mid-December.

Massachusetts only reports antigen tests administered at pharmacies or observed during telehealth visits. Still, the state registered a marked increase in that narrow category beginning in late November. Before Thanksgiving, the state reported an average of 12,000 to 15,000 rapid tests per day throughout the fall. After the onset of Omicron, that number crept closer to 30,000, peaking at 47,818 on Jan. 10.

Nevertheless, that data gives just a snapshot of the scope of rapid testing since it excludes all tests conducted at home without a proctor. The state’s Executive Office of Health and Human Services did not respond when asked whether Massachusetts plans to launch a rapid test reporting program.

What is desperately needed, said Howard Koh, a professor at the Harvard T.H. Chan School of Public Health, is a way to automatically connect rapid tests with health departments as opposed to clunky manually reported systems. Some antigen tests, such as the BinaxNOW home test, already have an option for users to scan a QR code and solicit a trained telehealth provider to proctor their test and send results to public health authorities.

“The absence of formal reporting systems for rapid test results exemplifies yet again the critical need for robust modern-day public health infrastructure and systems,” said Koh. “The states and cities that have launched online reporting systems are essentially building the plane while flying it. We need to be more proactive going forward to rebuild and revitalize public health from the ground up.”

With official case counts falling in the state, experts admit the ideal moment for implementing such a system in time to grasp the scope of Omicron may have passed.

“But let’s say we get a new variant. One that’s more infectious. More lethal. Evades the vaccine. Then all bets are off. We’ll have wished we put together a good reporting system that’s fast enough to help us pivot to combat its changes,” said Georges Benjamin, executive director of the American Public Health Association. “Days, weeks. Any heads-up with something like that would make a world of difference.”

Correction: A previous version of the story said that the Department of Public Health did not respond to inquiries about a future rapid test reporting system. In fact, the Department of Public Health directed the Globe to the Executive Office of Health and Human Services, which did not give comment for the story.