Comparison of PCR, Culture and Serologic Tests for Diagnosis of Mycoplasma pneumoniae Infection

Lee, Eun Young; Lee, Dong Jun; Lee, Jung A; Kim, Sung Won; Chang, Myoung Woong

Abstract

PURPOSE
For diagnosis of Mycoplasma pneumoniae infection, serological diagnosis, which is simple and rapid method, is uncertain to determine the reliable single serum titers. We compared serologic test, culture and polymerase chain reaction (PCR), and evaluated the reliable single titers of the specific serum antibody determination method for diagnosis of M. pneumoniae infection. METHODS: We included 73 pneumonic children between 3-11 years who were admitted to the pediatric department of St. Benedict hospital between November 2002 and July 2003. We used indirect particle agglutination test (Serodia-Myco II; Fujirebio, Tokyo, Japan) and serum specimens were obtained on admission and after 5-10 days. Fourfold rise of Mycoplasma antibody titers was considered as M. pneumoniae infection. We collected the throat swabs from all of the participants for culture and PCR. RESULTS: Of 73 patients, 41 patients met the diagnostic criteria by serologic test. PCR for M. pneumoniae was positive for 33 patients, sensitivity 80.5%, specificity 90.6%. M. pneumoniae was cultured from 24 patients, sensitivity 59%, specificity 100%. When cut-off was set at a titer of > or =1: 160, the sensitivity and specificity of PCR were significantly higher (61 % vs 68%) by receiver operation characteristic curve. (P=0.035) There was no correlation between culture method and Mycoplasma Ab titer. CONCLUSION: PCR is a highly sensitive and specific diagnostic method and enough to allow for early diagnosis in the acute phase. The single Mycoplasma Ab titer > or =1: 160 in child with respiratory symptoms is considered as M. pneumoniae infection and would be more sensitive, when combined with PCR.