Competing realities, uncertain diagnoses of infectious disease: Mass self-testing for COVID-19 and liminal bio-citizenship.

Diagnoses of infectious diseases are being transformed as mass self-testing using rapid antigen tests (RATs) is increasingly integrated into public health. Widely used during the COVID-19 pandemic, RATs are claimed to have many advantages over 'gold-standard' polymerase chain reaction tests, especially their ease of use and production of quick results. Yet, while laboratory studies indicate the value of RATs in detecting the SARS-CoV-2 virus antigen, uncertainty surrounds their deployment and ultimate effectiveness in stemming infections. This article applies the analytic lens of biological citizenship (or bio-citizenship) to explore Australia's experience of implementing a RAT-based mass self-testing strategy to manage COVID-19. Drawing on Annemarie Mol's (1999, The Sociological Review, 47(1), 74-89) concept of ontological politics and analysing government statements, scientific articles and news media reporting published during a critical juncture of the strategy's implementation, we explore the kind of bio-citizenship implied by this strategy. Our analysis suggests the emergence of what we call liminal bio-citizenship, whereby citizens are made responsible for self-managing infection risk without the diagnostic certitude this demands. We discuss how the different realities of mass self-testing interact to reinforce this liminal citizenship and consider the implications for the sociology of diagnosis.