肠道病毒A71型中和实验血清两倍稀释和四倍稀释的结果一致性评估

Agreement of EV-A71 neutralization assay:serial 4-fold versus 2-fold dilution comparison

目的:针对肠道病毒A71型(EV-A71)中和实验,评估血清稀释过程中采用两倍稀释和四倍稀释时在中和抗体滴度、几何平均滴度(GMT)、血清阳性率和新感染率等方面的一致性。方法:基于2013-2018年在湖南省安化县建立的1~9岁儿童和母婴前瞻性队列,采用分层抽样法抽取92名参与者共386份血清,对其同期进行两倍稀释和四倍稀释的EV-A71抗体中和实验。使用Bland-Altman法评估抗体滴度之间一致性;采用分层分析方法评估两种稀释方法对GMT、血清阳性率和新感染率的影响。结果:两种稀释方法中和实验所得抗体滴度平均差值为0.04(95% CI:-0.02~0.10),差异无统计学意义。两者一致性限度(LOA)的上下限(-1.12,1.21)(95% CI:-1.22~-1.02;1.10~1.31)均超过了临床可接受范围(-1,1),具有统计学意义( P<0.05)。两种稀释方法在全部人群和阳性人群的GMT及以血清阳转为定义的新感染率的差异分别为2、6和2%( P值均>0.05)。与两倍稀释中和实验相比,四倍稀释中和实验所得血清阳性率高6%(95% CI:1%~11%);当分别以“4倍升高”和“阳转/4倍升高”作为新感染定义时,四倍稀释中和实验所得新感染率分别高8%(95% CI:1%~16%)和 9%(95% CI:1%~17%)。 结论:两倍稀释和四倍稀释中和实验在估计GMT时,两者所得结果可比;但在评估人群新感染率时,两者之间的差异不可忽略。

Objective To evaluate consistency between 2-fold serial and 4-fold serial diluted neutralization tests against Enterovirus A71(EV-A71)in estimating titer,Geometric mean titer(GMT),seroprevalence,and seroincidence.Methods Based on a prospective cohort of 1-9 years old children,mothers and infants established in Anhua County,Hunan Province,during 2013-2018,from which 92 participants with a total of 386 blood specimens were sampled and tested with a 2-fold serial dilution and a 4-fold serial dilution neutralization tests against EV-A71 at the same time.Agreement was estimated using the Bland-Altman method.Stratified analysis was conducted to estimate effect dilution approach on GMT,seroprevalence and seroincidence.Results The mean difference(0.04,95%CI:-0.02-0.10)between the two dilution approaches was not significant.However,the limits of agreement(LOA)(-1.12-1.21),with the 95%confidence interval of upper LOA(1.10-1.31)and of lower LOA(-1.22--1.02),significantly exceeded the Clinic accept interval(-1,1)indicating insufficient agreement between the two approaches in practice.While the dilution approaches did not affect estimates of GMT of the total population and the positive population,and seroincidence with seroconversion only,the differences were 2,6 and 2%,respectively(P>0.05).Estimates of seroincidence with at least 4-fold increase and seroconversion/4-fold increase were significantly higher using a 4-fold dilution neutralization test compared to the 2-fold dilution neutralization test with 8%(95%CI:1%-12%)and 9%(95%CI:1%-17%),respectively.Conclusion The 2-dilution and 4-dilution neutralization tests yielded comparable results when estimating the population′s GMT;however,the difference between the two is not negligible when assessing the seroincidence.