Evaluation of five immunoassays and one lateral flow immunochromatography for anti-SARS-CoV-2 antibodies detection

IntroductionIn order to deal with the current pandemic caused by the novel SARS-CoV-2 coronavirus several serological immunoassays have been recently developed with the objective of being used as a complementary diagnostic tool and to support the RT-PCR technique currently considered the “gold-standard” method. However, these new assays need to be evaluated and validated. The purpose of this study was to assess the performance of five immunoassays (two ELISA and three CLIA assays) and one rapid immunochromatographic test for the detection of anti-SARS-CoV-2 antibodies.MethodsFive semiquantitative immunoassays (MENARINI®, PALEX®, VIRCLIA®, ROCHE® and SIEMENS®) and one lateral flow rapid test (WONDFO®) were performed. A total of 124 samples were studied. Case serum samples (n = 78) were obtained from COVID-19 patients confirmed by real-time RT-PCR/epidemiological-clinical-radiological criteria, and control non-SARS-CoV-2 samples (n = 46) belonged to healthy healthcare workers involved in a seroprevalence study.ResultsOverall, the tests showed sensitivities around 70–90% and specificities greater than 95%, including the immunochromatographic test. In addition, we observed very good agreements among them, being better for the detection of IgG than for IgM antibodies (Cohen's kappa index of 0.95 for VIRCLIA® IgG with ROCHE®), as well as good diagnostic power of the tests as determined by the ROC curves.ConclusionsThis study demonstrates the proper performance of the different immunoassays in order to be applied in the clinical practice as support in the diagnostic approach and in the development of vaccines and seroepidemiological studies of COVID-19.     

化学发光免疫分析检测丙肝病毒抗体在血液筛查中的应用评价

目的:评价化学发光免疫分析(CLIA)测定丙肝病毒(HCV)抗体的方法学性能在血液筛查中的应用。方法:以辣根过氧化物酶(HRP)为酶标记物,以鲁米诺为发光底物,采用双抗原夹心法检测血样中的抗-HCV。建立抗-HCV化学发光酶免疫分析方法,与常规使用的抗-HCV酶联免疫分析方法(ELISA)同时检测20例发光值(RLU)大于14 000的抗-HCV血清阳性标本,再用荧光定量RT-PCR检测;每天用卫生部临床检验中心指定生产的HCV的质控血清对CLIA进行检测,建立自己实验室的该项目临界值浓度,连续6个月对HCV质控血清检测,计算S/CO值,统计分析精密度、CV;用EQA的质控物检测HCV抗体,进行标本符合率计算。结果:CLIA方法的灵敏度为0.02ng/mL,阳性符合率为100%,ELISA的阳性符合率为75.2%,荧光定量RT-PCR检测的阳性符合率为100%。结论:HCV抗体CLIA检测抗-HCV试验方法的敏感性、准确性、稳定性较好,能满足临床输血早期筛查,以排除假阳性,杜绝漏检的风险。     

时间分辨免疫荧光法定量检测癌胚抗原(CEA)试剂临床应用研究

目的对自制时间分辨免疫荧光法定量检测癌胚抗原(CEA)试剂盒进行临床应用研究,为该试剂盒临床应用及临床疗效评价提供科学依据。方法收集血清标本326份,用自制试剂盒按试剂盒操作说明书对血样进行测定,并以化学发光法(R oche)为对照方法,W ALLAC公司的CEA时间分辨免疫测定药盒(A u toDELF IATMhCEA)作为复核试验,获取相关目标实验数据,并计算得“真实性”和“可靠性”等统计学数据。结果以化学发光法为对照试验,其阳性符合率为95.83%,阴性符合率为98.73%,检验无显著性差异;自制试剂盒的定量测定值与化学发光法的测定值较为一致,相关系数达0.93,相关性好。结论试剂盒检测性能与现在临床广泛应用的方法相仿,能满足临床应用的需要。     

乙型肝炎病毒表面抗原弱反应性标本的检测及临床意义

目的探讨乙型肝炎病毒表面抗原(HBsAg)弱反应性标本的临床检测对策及其临床意义。方法采用酶联免疫吸附试验(ELISA)试剂Ⅰ、Ⅱ和化学发光法分别检测155例HBsAg初检为弱反应性的标本。结果试剂Ⅰ与化学发光法的阳性符合率为47.1%,阴性符合率为5.2%;试剂Ⅱ与化学发光法的阳性符合率为13.5%,阴性符合率为39.3%;试剂Ⅰ与试剂Ⅱ的阳性符合率为25.2%,阴性符合率为7.1%。结论对于ELISA法检测HBsAg为弱反应性的标本,应分析原因并采用多家试剂及更灵敏的方法进一步复查以确认,最好是进行确认实验。     

Comparison of capillary earlobe and venous blood monitoring for occupational lead surveillance

Biological monitoring for occupational lead exposure involves routine venous blood draws from exposed employees. This uncomfortable procedure normally yields more blood than what is needed for analysis. Capillary blood sampling is less invasive but introduces the possibility of surface contamination. The objective of this study was to compare venous and capillary (earlobe) blood lead samples obtained from occupationally exposed individuals. Phlebotomists trained specifically in the collection of blood samples for lead determination collected 2 venous blood samples and 2 capillary earlobe samples from each participating employee. Before the capillary draw, the employee's earlobe was cleansed with an alcohol wipe in an effort to remove potential lead contamination. A second alcohol wipe was then used to sanitize the lancing area and was retained for lead analysis. Both the venous and capillary samples were subsequently analyzed with the use of graphite furnace atomic absorption spectrometry (GFAAS). GFAAS of venous blood specimens was considered the reference method of sampling and analysis. We collected and analyzed 126 paired earlobe and venous samples. Earlobe sampling was preferred to venous sampling by 54% of the employees surveyed. The mean difference between the capillary and venous results was 38.8 +/- 48.1 microg/dL. Lead concentrations in earlobe blood were more than twice those found in venous samples in more than half of the samples (64 of 126). Despite simple cleansing with an alcohol wipe and no visible skin contamination, 94% of the wipe samples from earlobes contained more than 1 microg of lead. Even low concentrations of contamination can significantly alter the concentration of lead in the blood; for example, sample contamination of 0.3 microg lead in a 200-microL blood sample would yield an increase of 150 microg/dL in the measured lead concentration. The findings of this study suggest that until satisfactory skin cleansing and decontamination techniques are identified and evaluated, earlobe sampling should be avoided in the surveillance of occupational blood lead levels.     

Comparison of the sensitivity of NAT using pooled donor samples for HBV and that of a serologic HBsAg assay

BACKGROUND: Studies were conducted using samples from early and late-stage HBV-infected persons to determine the pool size at which PCR had better sensitivity than a sensitive HBsAg chemoluminescence immunoassay (CLIA-HBsAg). STUDY DESIGN AND METHODS: HBV seroconversion panels were tested for HBsAg by CLIA and for HBV DNA by nested PCR (95% hit rate: 100 copies/mL); PCR was carried out at various dilutions. HBV serologically positive samples that were detected from the simultaneous screening of 540,161 routine whole-blood donations using CLIA-HBsAg and agglutination assays were also characterized for additional markers of HBV infection. RESULTS: In 9 of 10 HBV seroconversion panels, PCR had better sensitivity than CLIA-HBsAg at dilutions of 1-in-25 or lower. Of 65 CLIA-only confirmed-positive donor samples (agglutination assay-negative), 8 represented early infection, 2 of which were PCR positive at a 1-in-50 dilution but negative at a 1-in-100 dilution. Only 2 of 47 samples from probable late-stage HBV infection that were positive on CLIA only were PCR positive with 0.1-mL sample volume and the S-region primer; the remaining 45 samples required a 1.0-mL sample input and C-region primer for increased PCR positivity. The remaining 10 CLIA-only confirmed-positive donor samples were from HBV vaccine recipients. None of the 12 CLIA- and HBsAg-negative donor samples that were strongly anti-HBc reactive could be detected by PCR at any dilution; all 12 were PCR positive when undiluted, but 4 required a 1.0-mL input volume for PCR positivity. CONCLUSION: For the detection of samples representing early-stage HBV infection, PCR at dilutions of 1-in-25 or lower (equivalent to a pool of < or =25 members) had greater sensitivity than CLIA-HBsAg. In contrast, samples from late-stage HBV infection were detected by PCR only with undiluted samples (0.1-mL or 1.0-mL input volumes), regardless of CLIA-HBsAg reactivity. Therefore, although NAT using minipools of 25 donations or less may be effective for the detection of early-stage HBV infection, it may not be effective for the detection of persistent HBV infection.     

Mechanisms and biomarkers of immune quiescence in kidney transplantation

This review discusses the current understanding of biomarkers of immune quiescence based on reviews of published literature in kidney transplant operational tolerance and mechanistic studies based on a better characterization of the stable, well-functioning renal allograft.