The endogenous factors affecting the detection of serum SARS-CoV-2 IgG/IgM antibodies by ELISA.

To investigate endogenous interference factors of the detection results of novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) IgM/IgG. Enzyme-linked immunosorbent assay (ELISA) was used to detect SARS-CoV-2 IgM/IgG in sera of 200 patients without COVID-19 infection, including rheumatoid factor (RF) positive group, antinuclear antibody (ANA) positive group, pregnant women group, and normal senior group, with 50 in each group and 100 normal controls. The level of SARS-CoV-2 IgG in pregnant women was significantly higher than that in the normal control group (p = 0.000), but there was no significant difference between other groups. The levels of SARS-CoV-2 IgM in the pregnant women group, normal senior group, ANA positive group, and RF positive group were significantly higher than that in the normal control group (p < 0.05), with significant higher false-positive rates in these groups (p = 0.036, p = 0.004, p = 0.000, vs. normal control group). Serum RF caused SARS-CoV-2 IgM false-positive in a concentration-dependent manner, especially when its concentration was higher than 110.25 IU/L, and the urea dissociation test can turn the false positive to negative. ANA, normal seniors, pregnant women, and RF can lead to false-positive reactivity of SARS-CoV-2 IgM and/or IgG detected using ELISA. These factors should be considered when SARS-CoV-2 IgM or IgG detection is positive, false positive samples caused by RF positive can be used for urea dissociation test.

Chinese expert brief consensus on newborn screening of inherited metabolic disorders during the novel coronavirus infection epidemic.

Novel coronavirus (2019-nCov) infection (COVID-19) rapidly spread across China and 25 countries in the worldwide, which infected not only adults but also children, even neonates. Each year, about 15 million newborns are delivered in China. Newborn screening (NBS) helps effectively prevent some mental retardation, premature death, and adverse outcomes in the early stage of baby, which could detect some inherited metabolic disorders (IMDs). During this COVID-19 epidemic, how to balance the risk of infected 2019-nCov and the risk of disability and teratogenesis of IMDs. Expert members of NBS extra quality assessment in National Clinical Center of Laboratory (NCCL) give a brief consensus for NBS of IMDs in the COVID-2019 epidemic, hoping that the brief consensus could be reference for NBS of IMDs in the other epidemic areas or periods all over the world.