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Establishment of SARS-CoV-2 Immunoglobulins (IgM, IgG) Reference Intervals for Elder Population in China based on 3,733 Samples by Wencan Jiang, Yanan Liu, Guanghui Zheng, Hong Lv, Kelin Chen, Siwen Li, Lijuan Wang, Xuesong Liu, Yijun Shi, Guoge Li, Yaowei Ding, Guojun Zhang

Background: Establishment of reference intervals (RIs) for different biomarkers is essential for clinical monitoring. The purpose of this study was to establish laboratory RIs of SARS-CoV-2 IgM and IgG for elder population.
Materials: Performance verification was conducted with reference to the Clinical and Laboratory Standards Institute (CLSI) guidelines, including linearity, imprecision, and allowable dilution ratio. Based on CLSI C28-A3 document, a total of 3,734 serum samples were collected, and 3,733 serum samples were used for the establishment of RIs for SARS-CoV-2 IgM and IgG. The subjects were grouped by gender and age. The age groups were as follows: 60 - 69 years, 70 - 79 years, 80 - 89 years, and 90 - 101 years. The RI was defined by nonparametric 95th percentile intervals.
Results: Percentage deviation of all the seven dilutions were all less than 12.5% during linearity evaluation. The inter-assay and intra-assay imprecision were all less than 5%. There is no significant difference between different gender and age groups for IgM (p = 0.0818, p = 0.7094), and there is significant difference between different gender and age groups for IgG (p = 0.0011, p = 0.0013). Harris-Boyd’s test did not indicate partitioning for IgM and IgG. Cutoff values of RI for SARS-CoV-2 IgM and IgG were defined as 0.1523 S/CO and 0.2663 S/CO, respectively.
Conclusions: RIs of SRAR-CoV-2 IgM and IgG were established for elder population, which can play an important role in the prevention and control of the epidemic.

DOI: 10.7754/Clin.Lab.2022.211136