The UK government has adopted testing for antibody responses to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) proteins as a strategy for estimating the proportion of the population that has been infected, to better understand the spread of the virus. 1 The UK Rapid Test Consortium’s “AbC-19 TM Rapid Test”(AbC-19) detects the presence of IgG antibody against the trimeric SARS-CoV-2 spike protein in a finger prick device resembling a pregnancy test, allowing for rapid and scalable deployment in the community. Despite ongoing concerns, 2 the UK Government has committed to purchasing 1 million AbC-19 devices. 3

In the linked study commissioned by the UK government’s Department of Health and Social Care (doi: 10.1136/bmj. m4262), 4 Mulchandani and colleagues evaluate the accuracy of the AbC-19 assay and find that it may be considerably lower than previously suggested by an as yet unpublished study reported by Robertson and colleagues. 4 5