Japan approved Tuesday a polymerase chain reaction coronavirus test using saliva, which is much safer and easier compared to the currently dominant method that collects mucus from the back part of the nose.

The new testing method targets those within nine days of displaying symptoms and is covered by public health insurance. It is expected to pose less infection risk to medical staff as examinees only provide their saliva in a container at medical facilities.

The existing method uses a cotton swab to collect mucus from the nose, which has a high possibility of causing the patients to sneeze or cough in the process.

(Coronavirus tests known as PCR, or polymerase chain reaction, are shown to the media in Yokohama, near Tokyo, on May 23, 2020)

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As it leaves medical staff collecting the sample prone to potential infection, they need to wear goggles and gowns. This has become a sticking point in expanding the scale of the PCR test.

Japan has been widely criticized for not conducting enough virus tests compared to other countries.

"Both the burden on patients and sample-collecting institutions that need to protect staff from infections will be alleviated significantly," health minister Katsunobu Kato told a press conference.

The test will be available at outpatient departments at designated hospitals and PCR testing centers. It will also be used for patients with coronavirus symptoms and staff at medical institutions to avoid in-hospital infection.

There has been a concern that the amount of virus could be smaller in saliva than in mucus from the nose, resulting in the lower accuracy of its test results.

But research on specimens from 88 coronavirus patients found that the results were all but identical between the two methods for those within nine days of showing symptoms.

Biotech firm Takara Bio Inc. and precision equipment maker Shimadzu Corp. said their PCR test kits are compatible with saliva samples and that they will ramp up production of the kits.

Takara Bio already has the capacity to produce 2 million test kits a month. "We're eyeing further expansion of test kit production in preparation for a second and third wave of coronavirus infections," the company's spokesperson said.

Shimadzu, which has been selling test kits since April, raised its production capacity to 300,000 kits per month in early May from an initial 100,000 and is considering further boosting output this month.

Supplied photo shows a container for polymerase chain reaction coronavirus test using saliva. (Photo courtesy of the health ministry)(Kyodo)