Fig. 4: Operating characteristics of the HAT.
From: A haemagglutination test for rapid detection of antibodies to SARS-CoV-2
A The test set of 297 randomised plasma samples was diluted 1:40 and mixed with 1:40 O−ve blood in two columns. IH4-RBD (100 ng in 50 µL) was added to the test samples and PBS to negative control wells. The plates were incubated at room temperature for 1 h to allow the red cell pellet to form, then tilted for ~30 s to allow a teardrop to form. Complete loss of teardrop was scored as positive agglutination (marked with a black solid-line circle). Full teardrop or partial teardrop (marked with a dotted-line circle) was scored negative. The samples in columns were re-randomised and tested a second time 2 days later. B Contingency table showing the operating characteristics of the HAT. Source data are provided as a Source Data file.
