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目的探讨肺炎支原体(MP)荧光定量PCR检测在儿童MP肺炎(MPP)中的诊断价值。方法选择2008年6月-2009年1月住院的肺炎患儿153例,同期住院的非呼吸道感染患儿30例作为对照组。入选患儿均留取呼吸道分泌物(鼻咽深部分泌物、痰、肺泡灌洗液或咽拭子)和血清标本,部分患儿留取双份血清。采用MP荧光定量PCR法检测其呼吸道分泌物标本中MP DNA水平,用ELISA法和被动凝集法分别检测患儿血清MP-IgM抗体及MP抗体滴度。结果入选肺炎患儿中,MP抗体检测阳性(MPP)123例,双份血清MP检测阴性肺炎(非MPP)30例。MPP组:PCR阳性114例,PCR定量结果MP DNA水平为1.20×106～3.66×1010基因拷贝/L。非MPP组:PCR阳性2例,MP DNA水平为(1.08～3.02)×107基因拷贝/L。对照组:PCR结果均阴性。MPP患儿病程第1-2周,单份血清MP-IgM检测的敏感度仅为66.7%～83.9%,而定量PCR的敏感度为92.7%,特异度为93.3%;病程第3周后,单份血MP-IgM检测的敏感度上升为90.9%～100%。MPP组患儿入院时病程、住院时间及热程均显著长于非MPP组患儿,其临床表现无特异性。结论荧光定量PCR法较血清学方法更适用于MPP的早期快速诊断,2种方法结合既有利于早期诊断,又可提高诊断的准确性。
Objective To investigate the diagnostic value of Mycoplasma pneumoniae (MP) quantitative PCR in children with MP pneumonia (MPP). Methods 153 cases of pneumonia admitted in hospital from June 2008 to January 2009 were selected as the control group, and 30 cases of non-respiratory infection hospitalized in the same period were selected as control group. Selected children were taken for respiratory secretions (nasopharyngeal secretions, sputum, alveolar lavage fluid or throat swab) and serum samples, some children with double serum. The level of MP DNA in respiratory secretions was detected by MP fluorescence quantitative PCR. The titer of MP-IgM and MP in serum of children were detected by ELISA and passive agglutination respectively. Results Among the children with pneumonia, MP antibody was detected in 123 cases and negative serum MP was detected in 30 cases of negative pneumonia (non-MPP). In the MPP group, there were 114 positive cases of PCR. The quantitative PCR results showed that the MP DNA level was 1.20 × 106 ~ 3.66 × 1010 copies / L. Non-MPP group: PCR positive in 2 cases, MP DNA level (1.08 ~ 3.02) × 107 gene copies / L. Control group: PCR results were negative. In the first week 1-2 of MPP, the sensitivity of single serum MP-IgM was only 66.7% -83.9%, while the sensitivity and specificity of quantitative PCR were 92.7% and 93.3% respectively. After the third week of course, The sensitivity of single-blood MP-IgM test increased from 90.9% to 100%. The course of illness, length of hospital stay and duration of fever in MPP group were significantly longer than those in non-MPP group, and their clinical manifestations were nonspecific. Conclusion Fluorescence quantitative PCR method is more suitable than serological method for early rapid diagnosis of MPP. Combining the two methods not only facilitates early diagnosis but also improves the accuracy of diagnosis.