Heat inactivation of serum interferes with the immunoanalysis of antibodies to SARS‐CoV‐2

Abstract

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.

Clinical significance of the serum IgM and IgG to SARS‐CoV‐2 in coronavirus disease‐2019

“…The diagnose sensitivity was 82.86%, 90.48% and 96.19%, respectively. Hu et al 16 proposed heat‐treated serum samples could lead to false‐negative results of these samples. But this problem is not obvious in our research, and the sensitivity is acceptable.…”

“…8 Therefore, antibody test of suspected COVID-19 patients could be a good way that reduced missed diagnosis when RNA testing is negative. Lijia et al detected SARS-CoV-2 IgM and IgG antibodies in [15][16][17][18][19] patients. They found that the shortest time was 1.5-2 days for the detectable antibody after symptom onset.…”

Humoral Responses and Serological Assays in SARS-CoV-2 Infections

“…While this represents progress, what is ultimately required is a well-characterized set of standard sera that could be tested against any approved serology testing kit, allowing for the sensitivity and specificity of these kits to be compared (103). Other variables that require standardization for serological testing and kit comparisons include the length of time PSO for samples to be collected from patients, since the sensitivity and specificity of commercial tests can differ depending on the time at which the sample is collected (104), as well as the method by which samples are sometimes inactivated for lab safety (97,105).…”

Comparison of three automatic chemiluminescent immunoassays for monitoring dynamic profile of SARS‐CoV‐2 IgG and IgM

“…This might benefit the performance evaluation, decreasing the false‐positive results, it might as well underestimate the seroprevalence of SARS‐CoV‐2 antibodies. Safety operation with the infected serum also was important, and previous report showed the heat inactivation at 56°C significantly decreased the level of SARS‐CoV‐2 antibodies 23 . In the study, automatic CLIA system effectively reduced the professional exposing risk in compared with immunochromatographic assay when the infected serums are analyzed.…”