Comparison of enzyme Immunoassay with Immunofluorescence Assay for the Diagnosis of Mycoplasma pneumoniae Respiratory Tract Infections in Children

Abstract

Mycoplasma pneumoniae is a frequent cause of acute respiratory infections in both children and adults. Currently, diagnosis of M. pneumoniae infection will based principally on serology and the detection of IgM can provide an early and sensitive diagnosis in children. A variety of commercial immunodiagnostic assays, such as Indirect Enzyme-Linked Immunosorbent (ELISA) assay and Indirect Immunofluorescence (IFA), are now available as serological methods. The Aim of this comparative prospective study, was to compare two different approaches to the rapid detection of Mycoplasma pneumoniae respiratory tract infections among children. For this purpose, a commercial IFA assay for detection of M. pneumoniae-specific IgM antibody in acute-phase sera was used to compare with ELISA assay for specific-IgM antibody and to sought wither the use of either serological assays as a more reliable laboratory diagnosis for Mycoplasma pneumoniae respiratory tract infections in children. This study was designed as a comparative prospective study in which 90 patients (Mean age of the patients in case group was 5.94±2.73 and in control group was 6.51±2.26) of either sexes were included. These patients were classified into two groups: first group (case group), included 45 patients who had been admitted in hospital with diagnosis of respiratory tract infections and the second group (control group), included 45 healthy patients who had no history of respiratory tract infections. Both the groups were age and sex matched. Presence of IgM antibodies to Mycoplasma pneumoniae was assessed by IFA kit assay in both groups and the detection result was compared with result of previous study using ELISA assay. In the case group, 2 (4%) cases out of 45 children were positive for anti-mycoplasma antibody whereas in the control group, all children were negative. All positive case group patients had symptoms of acute pneumonia. 18 (40%) of the patients were diagnosed with bronchial asthma (40%) inclusive of all the two cases diagnosed with Mycoplasma pneumoniae infection. The IgM-positive rate for IFA assay (4%) was lower than in ELISA assay (9%), as compared from both kits. Taking the ELISA assay as a gold standard for the presence of Mycoplasma pneumoniae respiratory tract infections, the sensitivity, specificity and positive and negative predictive values of the IFA assay in comparison to ELISA, were 50 (CI:8.30 to 91.70%), 100 (CI:91.31 to 100%), 100 and 95.34% respectively. The results of IgM IFA assay showed relatively lower positivity than ELISA assay in the early acute phase, the results of IFA undertaken for the detection of M. pneumoniae respiratory tract infections and it is a first study in the Saudia Arabia of its kind from the region reporting such a disease in children using a serological assays as IFA and ELISA assays for comparasion . We therefore conclude that the use of ELISA assay conducted in the country as a more reliable laboratory diagnosis for Mycoplasma pneumoniae respiratory tract infections in children. Further future studies need to be carried out to investigate the use of PCR to allow fast and reliable diagnosis of M. pneumoniae infection during the early phases of infection in children.