Performance of rapid IgM-IgG combined antibody tests in the occupational surveillance of COVID-19 in Colombian enterprises

Introduction: Rapid IgM-IgG combined antibody tests can play an important role in the COVID-19 surveillance by supporting the diagnosis of infection, assessing the immune response, and verifying the progress towards herd immunity. Objective: To evaluate the performance of rapid IgM-IgG combined antibody tests in COVID-19 occupational surveillance in a group of Colombian enterprises. Materials and methods: We used the occupational surveillance data from companies that had performed periodic serological tests on all personnel from the end of April to the beginning of July, 2020. Workers were organized in small groups (“social bubbles”) to prevent outbreaks and optimize surveillance. The sensitivity was estimated as if the sampling had a prospective design. We describe here the changes in serological testing through periodic rounds.
Results: Data were obtained from 4,740 workers, of whom only 23 were symptomatic showing changes from IgM(-)/IgG(-) to IgM(+) and then to IgM(+)/IgG(+) and IgG(+). The sensitivity was 40.94% for IgM(+) and 47.95% for IgM(+)/IgG(+). This implies that a little less than half of the cases can be detected.
Conclusion: Antibody rapid tests have a role in the diagnostic process of infection and they must be evaluated taking into account the moment of the epidemic, the type of test purchased, and the populations at risk since their results depend on the number of infections and cases. In the context of a health crisis, they can be optimized by organizing workers into “social bubbles”