Analysis of viral load and convalescent antibody levels between individuals of COVID-19 with initial positive and re-positive nucleic acid test during the recovery period
Objective To study the characteristics of nucleic acid and antibody changes in COVD-19 individuals with initial positive and re-positive nucleic acid test(NAT).Methods The serum samples of 102 individuals with re-positive NAT and 165 individuals with initial positive NAT in the recovery period of a novel coronavirus infection outbreak were detected by chemiluminescence method.Real-time fluorescent RT-PCR method was used to detect viral nucleic acid.The basic information of all individuals came from China Disease Prevention and Control Information System-Infectious Disease Information Reporting Management System,including demographic characteristics,onset time,NAT results,etc.Perform statistical analysis on the data using SPSS 22.0.Results The recovery interval time for the individuals with re-positive NAT was concentrated between 31 to 60 days(78.43％),with 89.22％of individuals aged＜61 years old.The mean Ct values of ORFlab gene and N gene in re-positive NAT individuals were 34.99(33.63,36.87)and 34.81±2.28,respectively,which were higher than 26.73(23.25,33.13)and 27.67±5.54 in initial positive NAT individuals,and the differences were statistically significant(P＜0.05).The IgM,IgG antibody levels M(P25,P75)of the individuals with re-positive NAT were 0.32(0.01,1.09),152.45(89.09,231.84),neutralizing antibody levels M(P25,P75)were 3 157.87(1 635.99,3 550.26)AU/mL,respectively.The IgM,IgG antibody levels M(P25,P75)of the individuals with initial positive NAT were 0.41(0.13,1.07),134.85(65.03,245.36),and neutralizing antibody levels M(P25,P75)were 2 874.61(115.57,371.64)AU/mL,respectively,and the differences were not statistically significant(P＞0.05).Conclusions There were no significant differences in the levels of IgM,IgG and neutralizing antibody during the recovery period between the individuals with re-positive NAT and initial positive NAT.The viral load of re-positive NAT individuals is lower than initial positive NAT individuals,and the possibility of infection was relatively low.
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