• Research into the validity of using nasopharyngeal swab fluid and saliva in diagnosing COVID-19 has revealed a good diagnostic concordance rate between the two within nine days of the onset of symptoms. Based on this result, it was decided on June 2 that patients may take a saliva PCR test within nine days of the onset of symptoms.
• Since July 17, asymptomatic patients have also been allowed to use saliva-based tests.
• On April 27, 2020, a pharmaceutical application was submitted for FUJIREBIO Inc.'s antigen test kit "ESPLINE SARS-CoV-2." It was approved as Japan's first COVID-19 antigen test kit on May 13, 2020.
• After the antigen test kit's approval, a positive result was initially considered a definitive diagnosis, and a negative result required additional PCR testing for a definitive diagnosis. However, research results have since confirmed that the concordance rate for the antigen test kit results and the PCR test results was high for symptomatic cases from the second to the ninth day of the onset of symptoms.
Thus, the "Guidelines Regarding Use of SARS-CoV-2 Antigen Detection Kits" were reviewed on June 16. The use of nasopharyngeal swab fluid tests allows a definitive diagnosis to be made even if a negative test result is obtained for a patient from the second to the ninth day of the onset of symptoms.
• Qualitative antigen test kits were initially supplied by the Outpatient Services for Returnees and Contact Persons in prefectures with many patients and this was gradually expanded. These kits are now supplied nationwide regardless of the type of testing facility or medical institution.
Quantitative antigen test
• On June 19, FUJIREBIO Inc. obtained pharmaceutical approval for its new COVID-19 antigen detection kit "Lumipulse SARS-CoV-2 Ag." Insurance coverage for this kit began on June 25. By using special measuring equipment to provide a higher sensitivity than traditional antigen detection kits (qualitative antigen tests), this product can measure antigens quantitatively. Therefore, as with PCR tests, the nasopharyngeal swab fluid test can be used to obtain a definitive diagnosis regardless of whether the patient is symptomatic or asymptomatic.
• Saliva-based tests were originally allowed for patients within nine days of the onset of symptoms. As with PCR tests, however, the use of saliva-based tests has been allowed for asymptomatic patients as well since July 17.
'• Various antibody test kits are currently available on the Japanese market as research reagents, such as a rapid detection method called the immunochromatography method. However, care is required as the tests may be conducted using methods that do not demonstrate the expected level of accuracy.
'• Furthermore, no antibody test has been approved as an in vitro diagnostic medical device yet under the Act on Securing Quality, Efficacy and Safety of Products Including Pharmaceuticals and Medical Devices (Pharmaceutical Affairs Act) in Japan. The WHO suggests that although antibody tests should not be used on their own for diagnosis, they may be used for epidemiological investigations and other such purposes.
'• The antibody tests (general population survey) conducted by the MHLW use high-quality antibody testing equipment that meets international standards.
Antibody Test (General Population Survey) Overview (Japanese only) (Posted on May 29)
'• To determine the prevalence of antibodies in Japan, the MHLW randomly selected approximately 3,000 people by gender and age group from the general populations of three regions: Tokyo, Osaka, and Miyagi. It then conducted blood tests in the first week of June. As a result, the antibody possession rate was identified for each region.
Antibody Test Results (Japanese only) (posted on June 16)
'• With regard to the antibody tests published on June 16, 2020, the results of the neutralization test conducted by the National Institute of Infectious Diseases was announced.
Neutralization Test Results Obtained in the Antibody Test (Japanese only) (posted on July 14)
Reference: Performance evaluation for antibody test kits
'• The "Performance Evaluation for Antibody Test Kits" was put together and published by the AMED research group in cooperation with the Japanese Red Cross Society.
Performance Evaluation for Antibody Test Kits (Japanese only) (posted on May 15)