A fever-based therapeutic window for bronchoscopy to prevent bronchiolitis obliterans in children with Mycoplasma pneumoniae pneumonia.

Background: Flexible bronchoscopy is frequently used in children with severe or refractory Mycoplasma pneumoniae pneumonia (MPP), but the optimal timing of intervention remains uncertain. This study examined the nonlinear association between time from fever onset to bronchoscopy and post-infectious bronchiolitis obliterans (BO), and explored whether a timing interval associated with the lowest observed risk could be identified. Methods: In this retrospective cohort study, 332 children with laboratory-confirmed MPP who underwent flexible bronchoscopy during the index hospitalization were included. Restricted cubic spline modeling was used to evaluate the dose-response association between bronchoscopy timing and BO. Propensity score matching compared children treated within the spline-defined optimal window with those undergoing delayed bronchoscopy. Secondary outcomes included bronchoscopic complexity, post-bronchoscopy length of stay, and defervescence within 48 h. Results: Post-infectious BO occurred in 46 children (13.9%). BO incidence was lowest among children undergoing bronchoscopy at 4-5 days after fever onset and highest among those treated at ≥8 days. Restricted cubic spline analysis demonstrated a significant non-linear association between bronchoscopy timing and BO, with the lowest estimated risk around days 4-5 and a progressive increase after day 7. In the matched cohort, BO occurred in 7.4% of children in the 4-5-day group versus 22.1% in the delayed group, corresponding to a matched odds ratio of 0.28. The 4-5-day group also had lower bronchoscopic complexity, shorter post-bronchoscopy hospitalization, and higher 48 h defervescence rates. Conclusions: Bronchoscopy timing in pediatric MPP was nonlinearly associated with post-infectious BO, with the lowest observed risk around days 4-5.