Temporal dynamics of serum Mycoplasma pneumoniae antibodies in patients with acute respiratory infections: a large retrospective study

OBJECTIVE: Mycoplasma pneumoniae (MP) has re-emerged with a surging incidence in China following the lifting of COVID-19 non-pharmaceutical interventions, posing a critical challenge for clinical diagnosis and management of acute respiratory infections (ARI). We aimed to investigate the epidemiological characteristics of MP infection among all-age patients with ARI in China, as well as the temporal dynamics of serum MP-specific antibodies. METHODS: This retrospective study was based on the data of patients detected by total MP antibodies (predominantly IgM) in Chinese PLA General Hospital, Beijing, China between December 2022 and January 2024. Blood samples were collected from patients who visited or were hospitalized due to ARI for the detection of MP antibody. Adjusted odds ratio (aOR) and its 95% confidence interval (CI) were calculated to evaluate the association between MP antibody and outcome using logistic regression models adjusted by age groups, sex and diagnosis. RESULTS: Totally 18,054 patients were included in this study with the MP antibody detection rate of 36.2% (95% CI 35.5%-36.9%). The detection rate of MP antibody was higher in female than that in male (40.5% vs. 32.4%, aOR = 1.493, 95% CI 1.402-1.590, P < 0.001) and it was lower in adults compared to children (26.8% vs. 46.7%, aOR = 0.403, 95% CI 0.378-0.429, P < 0.001). The detection rate of MP antibody was the highest in the group of 10 ~ 20 years (53.7%, 95% CI 52.0%-55.4%). In all patients, the detection rate of MP antibody peaked at the 3rd week with 94.4% (95% CI 91.9%-95.0%), and then went down gradually, falling to 89.5% (95% CI 83.8%-95.1%) at the 8th week. The MP antibody peaked at the 1st week after symptom onset, followed by a gradual decline, and was predicted to turn to negative at about the 29th week. In children aged < 18 years, the interval between symptom onset and the MP antibody turning negative was about 24 weeks while it was 59 weeks in adults aged 18 ~ 59 years and 18 weeks in those aged ≥ 60 years. CONCLUSIONS: The detection rate of MP antibody differed in the patients with different characteristics. MP antibody could persist for 29 weeks and age was a significant factor affecting the duration of MP antibody. The lack of population representativeness and other relevant variables may have some impact on the results, but these findings still provided new evidence for the understanding of the epidemiology and immunology MP.