Role of Serum Mycoplasma pneumoniae IgA, IgM, and IgG in the Diagnosis of Mycoplasma pneumoniae-Related Pneumonia in School-Age Children and Adolescents

Mycoplasma pneumoniae is an important causative pathogen of community-acquired pneumonia in children. Rapid and reliable laboratory diagnosis ofM. pneumoniae infection is important so that appropriate antibiotic treatment can be initiated to reduce the misuse of drugs and resistance rates. Anti-M. pneumoniae immunoglobulin M (IgM) is an indicator of recent primary infection but can persist for several months after initial infection. It has been suggested that anti-M. pneumoniae immunoglobulin A (IgA) can be a reliable indicator for recentM. pneumoniae infection in adults. We investigated the clinical diagnostic value ofM. pneumoniae IgA in school-age children and adolescents withM. pneumoniae -related pneumonia. Eighty children with pneumonia and seropositive forM. pneumoniae IgM or with a 4-fold increase of anti-M. pneumoniae immunoglobulin G (IgG) were enrolled from May 2015 to March 2016. The titers ofM. pneumoniae IgA, IgM, and IgG, the clinical features, and laboratory examinations of blood, C-reactive protein, and liver enzymes were analyzed. The initial positivity rates forM. pneumoniae IgM and IgA upon admission to the hospital were 63.6 and 33.8%, respectively. One week after admission, the cumulative positivity rates forM. pneumoniae IgM and IgA increased to 97.5 and 56.3%, respectively. Detection ofM. pneumoniae IgM was more sensitive than detection ofM. pneumoniae IgA for the diagnosis ofM. pneumoniae -related pneumonia in school-age children and adolescents; however, paired sera are necessary for a more accurate diagnosis.