Background: The study was aimed to compare ELISA results of Mycoplasma pneumoniae IgG (MP-IgG) and Mycoplasma pneumoniae IgM (MP-IgM) with the passive particle agglutination (PA) test, as well as to evaluate their application value in the diagnosis of Mycoplasma pneumoniae pneumonia (MPP) in children.
Methods: Serum MP antibodies were detected by ELISA for MP-IgM, MP-IgG, and PA for 292 patients in the MPP group and 89 patients in NMP group. The PA results were used as reference standards. These patients were treated in the respiratory department of Children’s Hospital Capital Institute of Pediatrics, China, from July to December, 2019.
Results: In the MPP group, the positive rate for MP-IgM was 75% higher than that of the PA titer (73.97%), Pearson’s coefficient was 0.711, and the Kappa coefficient was 0.662, p < 0.01, suggesting that both the correlation and the consistency of the two methods were high. In the PA-negative group (< 1:160), 22.38% of patients were MP-IgM positive, indicating that the sensitivity to MP-IgM was higher compared to PA, when the disease duration was less than 7 days. The diagnostic value for MP-IgG was lower than that for MP-IgM, and the high positive rate of MP-IgG (48.31%) in the NMP group suggested a high background value of MP-IgG in children. Testing of paired serum obtained a more accurate diagnosis. At admission, 47.57% of patients with paired serum who were negative for MP-IgM, converted to a net positive after 4 – 6 days, except for one patient. In the paired serum, 57.8% of patients had a 4-fold increase of MP-IgG.
Conclusions: MP-IgM was a sensitive indicator of MP infection in children with a high consistency and correlation with the reference positive standard of PA titer ≥ 1:160. For a more accurate diagnosis, testing of paired serum is still necessary, and a 4-fold increase in MP-IgG could be the supplementary diagnosis method.