Figure 3
From: COVID-19 serological survey using micro blood sampling
taken from patients prior to November 2019. Sera from PCR positive individuals were collected at least 10–30 days post onset of symptoms.
Summary of OIST Serological Survey. (a) In assay step 1 (anti-RBD ELISA), 63 OIST samples were above the threshold (3 standard deviations above the average negative control). (b) All positives from step 1 were tested in step 2 (anti-spike ELISA). No OIST samples were above the threshold (4 times the average background). (c) Step-2 titers were measured at dilutions 1:100, 1:300, 1:900, 1:2700, and 1:8100. Positive controls showed much stronger signal than the OIST samples even at high dilution. The dotted line indicates the respective threshold level. All negative controls are samples
