Background The detection of serum antibodies to the severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) is emerging as a new tool for the coronavirus disease 2019 (COVID‐19) diagnosis. Since many coronaviruses are sensitive to heat, heating inactivation of samples at 56°C prior to testing is considered a possible method to reduce the risk of transmission, but the effect of heating on the measurement of SARS‐CoV‐2 antibodies is still unclear. Methods By comparing the levels of SARS‐CoV‐2 antibodies before and after heat inactivation of serum at 56°C for 30 minutes using a quantitative fluorescence immunochromatographic assay Results We showed that heat inactivation significantly interferes with the levels of antibodies to SARS‐CoV‐2. The IgM levels of all the 34 serum samples (100%) from COVID‐19 patients decreased by an average level of 53.56%. The IgG levels were decreased in 22 of 34 samples (64.71%) by an average level of 49.54%. Similar changes can also be observed in the non–COVID‐19 disease group (n = 9). Of note, 44.12% of the detected IgM levels were dropped below the cutoff value after heating, suggesting heat inactivation can lead to false‐negative results of these samples. Conclusion Our results indicate that heat inactivation of serum at 56°C for 30 minutes interferes with the immunoanalysis of antibodies to SARS‐CoV‐2. Heat inactivation prior to immunoanalysis is not recommended, and the possibility of false‐negative results should be considered if the sample was pre‐inactivated by heating.

The minor allele of the non-synonymous single nucleotide polymorphism (SNP) +1858C>T within the PTPN22 gene has now been unequivocally confirmed as conferring susceptibility to RA in population from Europe and America, but not in population from Asia. The aim of this study was to jointly address and integrate these separate findings to further elucidate the association between the PTPN22 gene and RA in Chinese Hans of Guangdong province. Four hundred and ninety-four cases with RA and 496 healthy controls were randomly selected, their SNPs at position -1123G>C (rs2488457), +1858C>T (rs2476601), +788G>A (rs33996649), and rs1310182 were genotyped using PCR-RFLP, followed by agarose gel electrophoresis. +1858C>T (rs2476601) and +788G>A (rs33996649) are not polymorphic in Chinese Hans. Meanwhile, our result reveals that the degree of association between the promoter polymorphism, -1123G>C and RA, was analogous to that observed in Japanese reports (odds ratio [OR] = 1.517, 95% CI = [1.154-1.995], P = 0.003). Expression study also indicated a tendency for association between -1123G>C and PTPN22 gene expression. Our study underpins that the promoter polymorphism, -1123G/C, may be a causal SNP for RA in Asian.

The detection of serum antibodies to the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is emerging as a new tool for the coronavirus disease-2019 diagnosis. Since many coronaviruses are sensitive to heat, heating inactivation of samples at 56