LAUSR

Serology testing of severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) is increasingly being used during the current pandemic of coronavirus disease 2019 (COVID‐19), although its clinical and epidemiologic utilities are still debatable. Characterizing these assays provides scientific basis to best use them. The current study assessed one chemiluminescent assay (Abbott COVID‐2 IgG) and two lateral flow assays (STANDARD Q [SQ] IgM/IgG Duo and Wondfo total antibody test) using 113 blood samples from 71 PCR‐confirmed COVID‐19 hospitalized patients, 119 samples with potential cross‐reactions, and 1068 negative controls including 942 pre‐pandemic samples. SARS‐CoV‐2 IgM antibodies became detectable 3‐4 days post‐symptom onset using SQ IgM test and IgG antibodies were first detected 5‐6 days post‐onset using SQ IgG. Abbott IgG and Wondfo Total were able to detect antibodies 7 to 8 days post‐onset. After 14 days post‐symptom onset, the SQ IgG, Abbott IgG and Wondfo Total tests were able to detect antibodies from 100% of the PCR‐confirmed patients in this series; 87.5% sensitivity for SQ IgM. Overall agreement was 88.5% between SQ IgM/IgG and Wondfo Total and 94.6% between SQ IgG and Abbott IgG. No cross‐reaction due to recent sera with three of the endemic coronaviruses was observed. Viral hepatitis and autoimmune samples were the main source of limited cross‐reactions. The specificities were 100% for SQ IgG and Wondfo Total, 99.62% for Abbott IgG, and 98.87% for SQ IgM. These findings demonstrated high sensitivity and specificity of appropriately validated SARS‐CoV‐2 serologic assays with implications for clinical use and epidemiological seroprevalence studies.