When Myles Cooper went in for a recent coronavirus test, a health care worker stuck a long, flexible swab deep into his nostril, spun it around gently for 10 seconds, and pulled it out from all the way in the back of his throat.

“My eyes started watering, I had to sit there for 30 seconds until I could see,” said Cooper, 37, who lives in San Francisco.

Cooper, who tested negative, is one of millions of people who have gotten tested for the coronavirus with a long, uncomfortable nasopharyngeal swab, which has been the standard way to test for respiratory illnesses. It collects specimens from the nasopharynx, which is where the nasal cavity and throat meet. Many people have also been tested with a long throat swab, known as an oropharyngeal swab.

But in recent weeks, many coronavirus testing sites have started using shorter, less invasive swabs that don’t go nearly as far into the nose. One type of swab, known as a mid-turbinate swab, penetrates about an inch to an inch-and-a half into the nostril until it hits resistance at the nasal wall. Another type goes into the front inside part of the nostril, called the anterior nares, about as far as someone would stick their pinky finger in to pick their nose.

The longer swab is still preferred by many health care providers, because questions remain about the accuracy of tests using the shorter swabs for asymptomatic people. But the shorter swabs are less unpleasant and in some cases can be used to collect samples by the patients themselves.

This is a significant development because if samples can be collected safely and accurately by patients themselves, it could make testing more accessible — opening the door for more home collection kits, and for health care workers at testing sites to use less personal protective equipment.

Swabs can be made from polyester, foam or nylon — and some health care providers say the materials used to make the shorter swabs are easier to obtain, given that longer swabs are still in demand around the world.

Experts say the less invasive swabs are about as good as the longer swabs at yielding reliable test results in symptomatic patients. But researchers are still studying whether they work as well in asymptomatic patients, who may have levels of virus in their nose that are too low to be detected in a test.

In late March, the CDC allowed health care providers to use the shorter swabs because the long swabs were nearly impossible to get at the time.

Verily, a South San Francisco life sciences company that has been contracted by the state to provide testing at 43 sites across California, began using shorter nasal swabs several weeks ago. Patients test themselves under the supervision of a health care worker. The company is transitioning from primarily using the longer swabs to primarily using the shorter nasal swabs because data indicates similar accuracy, a spokeswoman said. Having patients test themselves also reduces the risk of infecting health care workers because the longer swabs can prompt patients to cough or sneeze onto the health care worker who’s swabbing them.

Some of San Francisco’s city-run testing sites are also now primarily using shorter swabs.

“They are more comfortable for many people and can be self-collected, which decreases the amount of (personal protective equipment) used by providers at collection sites,” said Veronica Vien, a spokeswoman for the San Francisco Department of Public Health. “As testing science and technology rapidly evolves, we will continue to improve our response and testing efforts.”

OptumServe, a health services company contracted by the state to conduct testing in low-income and rural areas, is also using shorter nasal swabs for people 12 years old and younger.

Carbon Health, a San Francisco primary care company that is working with San Francisco to conduct much of the city-provided coronavirus testing, used long swabs at the start of the pandemic. It recently began using more of the shorter nasal swabs.

Three recent studies indicate that nasal samples self-collected by patients using shorter swabs are as accurate, or similar in accuracy, at detecting the virus as samples collected by health care workers using long swabs.

One study in Washington state, published June 3 in the New England Journal of Medicine, found that anterior nares swabs are just as accurate in diagnosing the coronavirus in symptomatic patients as nasopharyngeal swabs. It was published June 3 in the New England Journal of Medicine as a correspondence — a condensed form of reporting findings in the medical journal that is reviewed by the journal’s editors.

A second study, out of UCLA, found that oral and nasal specimens that were self-collected by patients using shorter mid-turbinate swabs generated results similar in accuracy to nasopharyngeal swab specimens collected by health care workers. The study, posted April 15, included mostly symptomatic patients. It is undergoing peer review.

Another study, published Friday in the Journal of the American Medical Association, found that symptomatic patients using shorter swabs to collect their own nasal samples yielded test results that were as accurate as samples collected by a health care worker using nasal and oropharyngeal swabs.

But researchers are still trying to determine if shorter nasal swabs are as good for testing asymptomatic patients who have levels of virus in their nose that may be too low to detect in a test. Researchers at UCLA and Stanford are examining this issue.

“So far it’s looking good. So far the problem, what we’re worried about, is if someone is asymptomatic, if you get nasal swab, will it be as likely to turn positive in a person who has a nasopharyngeal swab?” said Dr. Yvonne Maldonado, an infectious disease specialist at Stanford who led the JAMA study and is now studying whether shorter swabs are as good as longer swabs among asymptomatic patients. “Is there enough virus in the nose you’ll detect infection there? You don’t want to have a false negative. That’s what we’re doing now.”

Catherine Ho is a San Francisco Chronicle staff writer. Email: cho@sfchronicle.com Twitter: @Cat_Ho

Catherine Ho covers health care at The San Francisco Chronicle. Before joining the paper in 2017, she worked at The Washington Post, the Los Angeles Times and the Daily Journal, writing about business, politics, lobbying and legal affairs. She's a Bay Area native and alum of UC Berkeley and the Daily Californian.