Comparison of real-time polymerase chain reaction and serological tests for the confirmation of Mycoplasma pneumoniae infection in children with clinical diagnosis of atypical pneumonia.

BACKGROUND Mycoplasma pneumoniae is a common pathogen of respiratory tract infection in children, and its correct and rapid diagnosis is a clinical challenge. Real-time polymerase chain reaction (RT-PCR) has been used frequently for the detection of this pathogen. MATERIALS AND METHODS Medical records from all children with a clinical diagnosis of mycoplasma pneumonia and whose respiratory samples were tested for M. pneumoniae (using RT-PCR) during 2011 were reviewed retrospectively. We compared the sensitivity and specificity of serological assays versus those of RT-PCR for diagnosis of M. pneumoniae infections. We also reviewed retrospectively clinical characteristics, and laboratory and imaging findings of children with laboratory evidence of M. pneumoniae infection. RESULTS In 2011, 290 children were diagnosed to have mycoplasma pneumonia clinically and had their respiratory samples tested for M. pneumoniae by RT-PCR. Fifty-four children (19%) had a positive result. Meanwhile, 63% (182/290) of these children also underwent serological tests, out of whom 44 (24%) were found to be positive for immunoglobulin M (IgM). Using PCR as a gold standard, M. pneumoniae IgM assay was found to show a sensitivity of 62.2% and a specificity of 85.5%. Positive and negative predictive values of IgM were 52.3% and 89.9%, respectively. In M. pneumoniae IgM-positive children, a negative PCR result was associated with more coinfection by other pathogens and longer duration of prehospitalization fever. Bacterial loads of M. pneumoniae were not correlated with clinical outcomes. CONCLUSION The majority of clinically diagnosed mycoplasma pneumonia was unconfirmed. Mycoplasma pneumoniae IgM has poor sensitivity and a positive predictive value. Interpretation of Mycoplasma pneumoniae IgM should be done with caution.