Positive Ratio of Polymerase Chain Reaction (PCR) and Validity of Pre-Screening Criteria at an Outpatient Screening Center during the Early Phase of the COVID-19 Epidemic in Japan.

Despite the increase in COVID-19 cases globally, the number of cases in Japan has been relatively low, and an explosive surge in the prevalence has not occurred. In March 2020, the Ministry of Health, Labour and Welfare (MHLW) in Japan recommended the original criteria for polymerase chain reaction (PCR) testing, although there was a lack of evidence for appropriate targets for COVID-19 testing. This study aimed to evaluate the COVID-19 positive ratio and pre-screening criteria in Tokyo immediately after the insurance-covered SARS-CoV-2 PCR testing became available in Japan. We subjected 277 individuals with mild symptoms in metropolitan Tokyo (positive: 9.0%) from March 9 to 29, 2020, to SARS-CoV-2 PCR testing. The results revealed that 25 (9.0%) of them were PCR-positive. The sensitivity and specificity of the MHLW criteria were 100% and 10.7%, respectively. When the criteria excluded nonspecific symptoms, fatigue, and dyspnea, the sensitivity slightly decreased to 92%, and the specificity increased to 22.2%. The specificity was highest when the fever criterion was ≥37.5°C for ≥4 days, and exposure/travel history, including age and underlying comorbidities, was considered. Our findings suggest that the MHLW criteria, including the symptoms and exposure/travel history, may be useful for COVID-19 pre-screening.