上呼吸道感染患儿肺炎支原体IgM类与低亲和力IgG类抗体的测定

Detection of serum IgM and low affinity IgG antibodies against Mycoplasma Pneumoniae in children with respiratory tract infection

目的探讨上呼吸道感染患儿肺炎支原体(MP)IgM类(MP-IgM)与低亲和力IgG类(MP-IgG)抗体水平及在MP感染早期诊断中的价值。方法分别用被动颗粒凝集试验(PPA)、酶联免疫吸附试验(ELISA)和间接免疫荧光法(IIF)对小儿上呼吸道感染者血清MP-IgM水平进行测定,同时用IIF法研究其低亲和力MP-IgG水平,对所测结果进行对比研究。结果3种方法所测MP-IgM以ELISA法阳性率最高(60.0%,51/88),PPA法次之(50.0%,44/88),而IIF法最低(40.9%,36/88)。各方法间仅PPA法与ELISA法所测结果具有显著相关(P<0.001)和中等程度的一致性(0.7>Kappa>0.4),而PPA法与IIF法、ELISA法与IIF法检测结果缺乏一致性。88例患儿中,有21例(23.9%)存在低亲和力MP-IgG抗体,其中17例同时有MP-IgM阳性,两者结果亦具有显著的相关(P<0.001)和一定程度的一致性(0.7>Kappa>0.4)。结论低亲和力MP-IgG类抗体有类似于MP-IgM类抗体的早期诊断价值,与MP-IgM联合检测有助于区分MP近期感染与感染后复发或再次感染。

Objective To investigate the serum levels of IgM and low affinity IgG antibodies against Mycoplasma Pneumoniae （MP） in children with respiratory tract infection, and explore the value of the detection in early diagnosis of children＇ s MP infection. Methods Serum levels of MP-IgM antibody in children with respiratory tract infection were measured by using three methods：pellet agglutination assay （PGA） ,ELISA and indirect immuno-fluorescence（IIF） technique. Meanwhile, low affinity MP-IgG antibody was also detected by IIF. The serum levels of MP-IgM and low affinity MP-IgG antibodies were parallelly investigated. Results Serum levels of MP-IgM antibody were different due to discrepancy of test methods. 60.0% （51/88） of cases was positive by ELISA, 50.0% （44/88） of cases was positive by PGA, and 40.9% （36/88） of cases was positive by IIF. The result had significant association and moderate coincidence between PGA and ELISA （0.7 〉 Kappa 〉 0.4, P 〈 0.001 ）, whereas the results between PGA and IIF, ELISA and IIF were inconsistent. 21 of all infective cases were higher levels of low affinity MP-IgG antibody （23.9% of positive cases）, among whom 17 of 21 cases were synchronously accompanied by positive MP-IgM antibody, and both also had significant association and moderate coincidence （0.7 〉 Kappa 〉0.4, P 〈 0. 001 ）. Conclusion Low affinity MP-IgG serves as a serum parameter of MP infection, provided with early diagnosis value analogous to MP-IgM antibody. So, the results of the assay were significantly important for distinguishing MP early infection, relapse after infection and second infection.