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. 2020 Sep;34(9):e23411.
doi: 10.1002/jcla.23411. Epub 2020 Jun 28.

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

Xiumei Hu  1   2 , Taixue An  1   2 , Bo Situ  1 , Yuhai Hu  3 , Zihao Ou  1 , Qiang Li  1   2 , Xiaojing He  1 , Ye Zhang  1 , Peifu Tian  3 , Dehua Sun  1 , Yongyu Rui  1 , Qian Wang  1 , Dan Ding  4 , Lei Zheng  1   2
Affiliations

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

Xiumei Hu et al. J Clin Lab Anal. 2020 Sep.

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.

Keywords: COVID-19; SARS-CoV-2; antibodies; heat inactivation; immunoanalysis.

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Figures

Figure 1
Figure 1
The changes in the IgM and IgG levels of the 34 serum samples from patients with COVID‐19 infections detected by AFIA before (blue dot) and after heat inactivation (red dot). Dash line indicates the cutoff value of the assay
Figure 2
Figure 2
The changes in the IgM and IgG levels of 9 serum samples from non–COVID‐19 group detected by AFIA before (blue dot) and after heat inactivation (red dot)
See this image and copyright information in PMC

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