The government is considering starting antibody testing as early as this month to check for a history of infection with the new coronavirus, The Yomiuri Shimbun has learned. The government aims to better understand the spread of the disease in each region. Several thousand people are to be selected for the testing. The health ministry plans to announce the outline of the testing as early as next week.

The currently used polymerase chain reaction (PCR) tests look for viruses in the patient’s body at the time of the test. Antibody testing, on the other hand, determines whether antibodies for the virus have developed after infection.

PCR testing is performed on patients when deemed necessary by doctors. However, experts point out that the number of tests done has not kept up with the spread of the infection, and the situations of the epidemic in Japan’s regional areas are not well understood. The fact that there are many people with mild or no symptoms among those infected with the coronavirus — and that such people aren’t subject to PCR tests — also makes it difficult to grasp the actual situation. The government has concluded that antibody testing to check the immune response after an infection will be useful in determining the current situation of the disease.

Antibody testing can be performed by blood sampling and results can be obtained in about 10 to 15 minutes. This means the antibody tests could be carried out in much greater numbers than PCR tests, which take about six hours. The Health, Labor and Welfare Ministry is holding accelerated discussions on the age, region and implementation procedures to be covered by the testing. The ministry is also considering allowing inpatients to be discharged from hospitals if they are found to have antibody responses, intending to relax current criteria that require two negative PCR tests for discharge.

The United States and European countries have already announced plans to launch antibody testing. The U.S. National Institutes of Health has announced a plan to carry out the testing on about 10,000 people who have not been confirmed to be infected with the virus. Britain also has already announced its intention to implement antibody testing.

However, the accuracy of antibody testing remains questionable. The World Health Organization said it is unclear how much immunity convalescing people have, given that there have been confirmed cases in which people with coronavirus tested positive again after recovering. In Japan, the Japanese Association for Infectious Diseases is analyzing the effectiveness of the testing, but many government officials are cautious about using the test results as the basis of an exit strategy, such as easing requests to refrain from going out.