Evaluation of serum IgM and IgG antibodies in COVID‐19 patients by enzyme linked immunosorbent assay. Issue 5 (1st March 2021) - Zhou, Chang
Abstract: Severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) is sweeping the world since the end of 2019. The titer change of antibodies against SARS‐CoV‐2 needs to be further clarified, the clinical and preventive value of antibodies still needs to be further investigated. An enzyme‐linked immunosorbent assay (ELISA) was established by coating with SARS‐CoV‐2 recombinant spike protein and used to detect serum immunoglobulin M (IgM) and immunoglobulin G (IgG) antibodies against SARS‐CoV‐2 in coronavirus disease 2019 patients to evaluate the pattern of changes of antibodies. The specificity of the ELISA for detection SARS‐CoV‐2 IgM and IgG were 96% (144/150) and 100% (150/150), respectively. The sensitivity of ELISA was 100% (150/150) for IgM, and 99.3% (149/150) for IgG. SARS‐CoV‐2‐SP‐IgM and SP‐IgG antibodies could be detected on Day 1 of hospitalization in 12.5% patients, and SP‐IgM began to decrease after reaching its peak at around 22–28 days, and become negative at Month 3 in 30% patients and negative at Month 7 in 79% of these patients after onset; IgG reached its peak around Day 22–28 and kept at a high level within the longest observation period for 4 months, it dropped very sharply at 7 months. The positive rates of SP‐IgM and SP‐IgG were higher than those of reverse transcription‐polymerase chain reaction on Day 7 and 4. The established indirect ELISA has good specificity and sensitivity. IgM and IgG against SARS‐CoV‐2 appeared almost simultaneously in the early stage, and the level of IgG antibodies could not maintain a high plateau in the observation period of 7 months. Our data will help develop the diagnosis and vaccine of SARS‐CoV‐2.