献血者HIV ELISA反应性标本的结果分析及其灰区设置的探讨

Analysis of HIV ELISA reactive samples and corresponding grey zone

目的探讨无偿献血者抗-HIV ELISA双试剂检测结合血液核酸检测(NAT)应用后ELISA(试剂)有无必要设置灰区。方法回顾性收集江苏省血液中心2010年6月—2017年8月采用2种HIV ELISA试剂(分别为第3、4代试剂)筛查反应性、并经核酸检测(NAT)和蛋白免疫印迹(WB)确证试验的585(人)份献血者标本,根据HIV ELISA初筛S/CO值和WB确证试验结果建立受试者工作特征曲线(ROC曲线),确定ELISA检测最适临界值;分析HIV ELISA检测反应性标本的NAT及WB确证结果,比较灰区临界值及厂商推荐临界值判定的反应性标本的确认阳性率。对抗-HIV不确定的8名献血者进行追踪并重新采样,根据追踪标本的检测结果确定其HIV感染状况。结果所用第3、4代HIV ELISA试剂最大约登指数对应的最适临界值分别为9.783和9.084;0.5≤S/CO<1灰区反应性标本确证试验结果均为阴性。第3、4代ELISA试剂双反应性且NAT阳性标本的WB确证试验阳性率91.24%(125/137);8例WB结果不确定标本中,有4例为ELISA单试剂反应性、NAT反应性且WB结果不确定,对其中3名献血者成功随访,随访时间3—8周,追踪检测≥2次,3人抗-HIV均转阳。结论采用第3、4代抗-HIV ELISA试剂检测不必设置灰区,第4代抗-HIV ELISA试剂检测结果结合NAT结果,可作为HIV窗口期感染和WB不确定结果献血者追踪检测的重要依据。

Objective To discuss the necessity of ELISA grey zones in joint tests of dual-reagent HIV ELISA and nucleic acid test(NAT). Methods 585 blood samples recorded during June 2010 to August 2017 were retrospectively studied, which were reactive samples in dual-reagent(third and fourth generation reagents respectively) ELISA tests and further screened by NAT. Western Blot(WB) was performed in addition as well. The receiver operating characteristic curve(ROC curve) was established based on the S/CO values of ELISA preliminary screening and confirmation results to verify the optimal cutoff(CO) value of ELISA. The NAT and WB results of ELISA reactive samples were analyzed. The confirmed positive rates were compared to samples yielded by grey zone CO or the manufacturer’s recommended CO. 8 blood donors were followed up with ambiguous WB results. The HIV infection status was determined according to the final follow-up results. Results For the 3 rd and 4 th generation ELISA reagents, the Youden index obtained a maximal peak when the S/CO values stayed at 9.783 and 9.084. Cases of S/CO value in the 0.5—1(grey zone) were confirmed negative. In dual-reactive cases, 91.24%(125/137)were confirmed positive of HIV-1 antibody, and HIV RNA positive. Among 8 unconfirmed samples, 4 were single reagent reactive and NAT positive. 3 of the 4 were followed up for 3—8 weeks with more than 2 further tracking tests, yielding positive results. Conclusion grey zone in the HIV screening test by ELISA is not required and serves little significance in a dual-reagent system. The combination the fourth-generation HIV assay and NAT screening results offers reliable evidence for the confirmation of HIV window period infections and donor follow-ups.