Case Screening Criteria for Early Detection of COVID-19 Cases in the First Wave of the Pandemic, Thailand

Abstract

In response to the emerging threat of a global pandemic, on 4 Jan 2020, Thailand became one of the first countries to activate a national emergency operations center for what was later to be known as the COVID-19 response. On 8 Jan 2020, just four days later, the first COVID-19 case outside of China was detected at an international airport in Thailand. As prompt detection of cases is critical to mitigate transmission, identifying the optimum case screening criteria for RT-PCR testing for SARS-CoV-2 was a priority for the Thai government, but also a challenge given the non-specific symptoms associated with COVID-19. Eight case screening criteria (CSC) were applied over four months. This study describes Thailand's COVID-19 CSC, the validity of individual criteria, and provides acceptable sensitivity for future waves by analyzing retrospective surveillance and laboratory data reported through Thailand’s national surveillance system. Between 4 Jan and 26 Apr 2020, 1,209 hospitals reported 53,068 individuals who were laboratory tested for COVID-19. Of these, 20,061 (37.8%) met at least one of the criteria and the number of confirmed cases was 2,922. Each criteria was sensitive to detect confirmed cases (overall sensitivity=83.3%). There were no significant differences between individual criteria (p>0.05), and a low positive predictive value (12.1%) indicated that the criteria were broad. The criteria were regularly revised to improve COVID-19 detection and response. The acceptable sensitivity of these criteria should be monitored regularly and should be more than 80% for disease detection and subsequently trigger the immediate response.