Lafarga B, Noguera F J, Pérez M C, Copado R, García A, Soria E
Servicio de Microbiología, Hospital Nuestra Señora del Pino, Las Palmas de Gran Canaria.
Enferm Infecc Microbiol Clin. 1998 Nov;16(9):413-8.
It is necessary to have an easy and quickly test to distinguish "false positive" rubella IgM results and residual antibodies from the antibodies produced in the primary infection, in pregnant women. The avidity of IgG antibodies test seems to differentiate between primary rubella infection and past infections, reinfections or postvaccination, showing its utility in the diagnosis of primary infection in other infectious diseases.
For 30 months, 178 sera from 157 patients with clinical and/or epidemiological rubella suspicion or with a positive rubella IgM result as result of an accidental serological finding, were remitted to our laboratory for a serological follow up. We distinguished 3 patient groups: outbreak group, 112; pregnant women, 36, and newborn 11. Rubella IgM antibodies by indirect EIA previous the rheumatoid factor absorption; IgG antibodies of low avidity by indirect EIA previous treatment of serum with 6 M urea, were detected in the sera. It considered a positive result, a rubella avidity index (AI) < 50%.
In the epidemic outbreak group, 90.2% of the patients were not vaccinated. 80% of cases occurred in young men between 14 an 20 years old. From 109 patients (97.3%) with rubella IgG antibodies, 92 (84.4%) showed AI-IgG lower than 50%. In this group, the mean rate of AI-IgG rubella was 29.0%. In the pregnant women group, except for two of them, rubella IgM antibodies were an accidental finding in a serological pregnancy screening. Thirty patients (83.8%) showed AI-IgG rubella > 50%. The two pregnant women who had evidence of clinical and epidemiological rubella showed AI-IgG rubella of 37.4% and 20.9%. Another four pregnant women showed AI-IgG rubella close to cut-off (44.7-49.0%). The mean AI-IgG rubella in this group was 71.8%. The mean AI-IgG Rubella between the epidemic outbreak group and the pregnant women group, 29.0 and 71.8% respectively, was statistical significance (p < 0.001).
The avidity IgG test is simple and quickly, and it allow to exclude most of positive results because of residual IgM antibodies and false reactive.
对于孕妇而言，需要一种简单快速的检测方法来区分风疹IgM结果“假阳性”以及原发性感染产生的抗体中的残留抗体。IgG抗体亲和力检测似乎可以区分原发性风疹感染与既往感染、再感染或疫苗接种后情况，显示出其在其他传染病原发性感染诊断中的效用。
在30个月的时间里，将157例临床和/或流行病学上疑似风疹或因偶然血清学检查风疹IgM结果呈阳性的患者的178份血清送至我们实验室进行血清学随访。我们将患者分为3组：暴发组，112例；孕妇，36例；新生儿，11例。通过间接酶免疫测定法在类风湿因子吸收前检测血清中的风疹IgM抗体；通过间接酶免疫测定法在用6M尿素处理血清前检测低亲和力的IgG抗体。风疹亲和力指数（AI）<50%被视为阳性结果。
在疫情暴发组中，90.2%的患者未接种疫苗。80%的病例发生在14至20岁的年轻男性中。在109例（97.3%）有风疹IgG抗体的患者中，92例（8又4.4%）的AI-IgG低于50%。在该组中，风疹AI-IgG的平均率为29.0%。在孕妇组中，除2例患者外，风疹IgM抗体是在血清学妊娠筛查中偶然发现的。30例（83.8%）患者的风疹AI-IgG>50%。有临床和流行病学风疹证据的2例孕妇的风疹AI-IgG分别为37.4%和20.9%。另外4例孕妇的风疹AI-IgG接近临界值（44.7 - 49.0%）。该组中风疹AI-IgG的平均值为71.8%。疫情暴发组与孕妇组之间风疹AI-IgG的平均值分别为29.0%和71.8%，具有统计学意义（p<0.001）。
IgG亲和力检测简单快速，能够排除大多数因残留IgM抗体和假反应导致的阳性结果。
