尿素解离法降低新型冠状病毒IgM和IgG检测结果假阳性的效果评价

Effect of Urea Dissociation on Reducing the Number of False⁃Positive Results of IgM and IgG Antibodies Against SARS⁃CoV⁃2

探讨引起新型冠状病毒(SARS-CoV-2)免疫球蛋白M(IgM)和免疫球蛋白G(IgG)抗体检测结果假阳性的干扰因素,改良检测方法,完善实验室检测方案。本研究收集2020年1月2日至2020年3月5日就诊于川北医学院附属医院及南充市中心医院的门诊及住院患者血清样本共74份,其中19例为SARS-CoV-2核酸检测确诊阳性,10例为其他呼吸道病毒IgM抗体阳性,10例肝炎病毒抗体IgM阳性,20例类风湿因子IgM阳性,15例抗核抗体阳性。采用胶体金免疫层析法(试剂A、试剂B)分别对研究对象血清进行SARS-CoV-2 IgM和IgG抗体检测,并对结果为SARS-CoV-2 IgM或SARS-CoV-2 IgG阳性的病例进行分析,发现造成检测结果假阳性的可能因素。再采用合适浓度的尿素对检测为阳性结果的血清及3例SARS-CoV-2 IgM阳性的COVID-19早期患者血清进行解离,解离后分别重新测定SARS-CoV-2 IgM、IgG抗体。采用SPSS19.0统计软件对数据进行统计学分析。结果显示,19例COVID-19确诊患者血清中,试剂A检出SARS-CoV-2 IgM、IgG抗体阳性数为15例及18例,试剂B检出SARSCoV-2IgM、IgG抗体阳性数均为12例;20例类风湿因子IgM阳性患者血清中,试剂A检出SARS-CoV-2IgM、IgG抗体阳性数为16例及14例;15例高滴度ANA阳性患者血清中,试剂B检出4例SARS-CoV-2 IgG抗体阳性。尿素解离浓度为2 mol/L时,试剂A检出的RF-IgM阳性血清中的16例SARS-CoV-2 IgM抗体有14例转阴,14例SARS-CoV-2 IgG抗体有13例转阴,而试剂A在COVID-19确诊患者血清中检出的SARS-CoV-2 IgM、IgG抗体均未出现阴转;尿素解离浓度为4 mol/L时,试剂B检出的ANA阳性血清中的4例SARS-CoV-2 IgG抗体全部转阴,而在COVID-19确诊患者血清中检出的的SARS-CoV-2 IgM、IgG抗体均未出现阴转。另外,经过尿素解离后,试剂A和试剂B在3例COVID-19早期患者血清中检出的SARS-CoV-2 IgM抗体也都未出现阴转。本研究提示,IgM型类风湿因子易造成试剂A检测血清SARS-CoV-2 IgM、IgG结果的假阳性;高滴度的ANA抗体也会引起试剂B检测血清SARS-CoV-2 IgG结果的假阳性。对检测结果假阳性的样本,采取尿素解离方案,能有效降低检测过程中假阳性发生的概率;尿素解离法对COVID-19患者发病早期标本检测灵敏度的影响尚待进一步深入研究。

We wished to explore the interference factors causing false-positive results for immunoglobulin M(IgM)and IgG antibodies in severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)detected by the gold immunochromatography assay(GICA).In this way,we wanted to improve the detection method and scheme of laboratory detection.Seventy-four serum samples from outpatients and inpatients from the Affiliated Hospital of North Sichuan Medical College and Nanchong Central Hospital in China from 2 January 2020 to 5 March 2020 were collected:19 patients with the nucleic acids of SARS-CoV-2;10 cases with IgM antibodies against other respiratory viruses;10 patients with IgM antibodies against hepatitis viruses;20 patients with IgM antibodies against rheumatoid factor(RF);15 patients with antinuclear antibody(ANA).Colloidal GICA(kit A and kit B)was used to detect IgM and IgG antibodies against SARS-CoV-2 in patient sera.Positive results of SARS-CoV-2 IgM or SARS-CoV-2 IgG antibodies were analyzed,and possible factors causing false-positive results were found.Then,the sera of SARS-CoV-2 IgM/IgG positive and 3 early COVID-19 patients were dissociated with an appropriate concentration of urea,and levels of IgM and IgG antibodies against SARS-CoV-2 were redetermined.SPSS v19.0 was used to analyze data.In the sera of 19 patients with SARS-CoV-2 infection:15 of SARS-CoV-2 IgM antibodies and 18 cases SARS-CoV-2 IgG antibodies were detected in kit A;12 cases of SARS-CoV-2 IgM antibodies and 12 cases of SARS-CoV-2 IgG antibodies were detected in kit B;16 cases of SARS-CoV-2 IgM antibodies and 14 cases of SARS-CoV-2 IgG antibodies were detected in 20 patients who had IgM antibodies against RF.In the sera of 15 patients with high-titer ANA,SARS-CoV-2 IgG antibodies were detected in four cases using kit B.When the urea dissociation concentration was 2 mol/L,14 of 16 RF-IgM-positive sera detected using kit A turned negative,13 of 14 SARS-CoV-2 IgG antibodies turned negative,but patients with coronavirus disease 2019(COVID-19)detected by kit A did not show negative conversion of IgM or IgG antibodies.When the urea dissociation concentration was 4 mol/L,ANA-positive serum detected by kit B turned negative in four cases,whereas SARS-CoV-2 IgM and IgG antibodies in patients with COVID-19 did not turn negative.After urea dissociation,the SARS-CoV-2 IgM antibodies detected by kit A and kit B in the sera of three patients with early COVID-19 did not turn negative.RF could cause false-positive results for SARS-CoV-2 IgM and IgG antibodies detected by kit A,and a high titer of ANA could cause false-positive results of SARS-CoV-2 IgG antibodies detected by kit B.Urea dissociation could be helpful for reducing the probability of false-positive results of SARS-CoV-2 IgM and IgG antibodies.The effect of urea dissociation on the detection sensitivity of early COVID-19 merits further study.