Fig. 2

P/N ratios for the positive controls, negative controls, and testing data, jittered horizontally. Cutoffs as calculated by each of the seven methods are shown as horizontal lines. The first row shows the spike test cutoffs with a a target specificity of 0.995 and b a target specificity of 0.95. The second row shows the receptor-binding domain (RBD) test with c a specificity of 0.995 and d a target specificity of 0.95. Training data was sampled from staff at long-term care facilities in Colorado, USA between June and December 2020. Testing data collected from skilled nursing staff in Colorado during May 2020