Poor accuracy of single serological IgM tests in children with suspected acute infection in Guangzhou, China.

Early and accurate diagnosis of () infection of children with pneumonia is at the core of treatment in clinical practice. Serological immunoglobulin M (IgM) tests for infection of children in south China have been rarely described. To assess the diagnostic performance and clinical application of serodiagnosis of infection in paediatric pneumonia patients. Serum samples from 144 children diagnosed with pneumonia were subjected to a particle agglutination (PA)-based IgM assay. Meanwhile, we used an established suspension array as the reference standard method for the detection of DNA in bronchoalveolar lavage fluid (BALF) from all patients to assess the reliability of serological assays. When running immunological testing in single serum samples, 80.6 %(79/98) of cases were diagnosed with infection, whereas only 55 (56.1 %) cases were positive in DNA analysis. Furthermore, single serum tests for IgM during acute infection resulted in 85.5 % (47/55) sensitivity and 25.6 % (11/43) specificity. Nevertheless, immunological testing and DNA analysis yielded the same results when paired sera were available for IgM antibody testing. Paired serological IgM assays are necessary for the determination of an acute infection, whereas single serological IgM testing is unreliable. Moreover, even a short interval of two serological tests works well.