Risk factors associated with plastic bronchitis in children with severe Mycoplasma pneumoniae pneumonia: a systematic review and meta-analysis.

BACKGROUND: Plastic bronchitis (PB) represents a severe complication of Mycoplasma pneumoniae pneumonia (MPP) in pediatric populations, characterized by the formation of obstructive bronchial casts. Early identification of risk factors is essential for timely bronchoscopic intervention and improved clinical outcomes. However, existing primary studies have reported inconsistent findings regarding the strength and significance of individual risk factors, likely attributable to heterogeneous study designs, varying predictor definitions and cut-off values, and differences in population severity criteria. No comprehensive meta-analysis has systematically synthesized this evidence to date. This study aimed to systematically evaluate and quantitatively synthesize evidence on risk factors associated with PB in children with severe (SMPP) or refractory (RMPP) MPP, with particular focus on inflammatory biomarkers, radiological features, and clinical characteristics.

METHODS: A systematic literature search was conducted across PubMed/MEDLINE, Embase, Web of Science, Scopus, and Cochrane Library (January 1, 2015, to December 1, 2025). Case-control and cohort studies reporting risk factors for bronchoscopically confirmed PB in pediatric SMPP or RMPP patients were included. Methodological quality was assessed using the Newcastle-Ottawa Scale (NOS). Random-effects meta-analysis was performed using the DerSimonian-Laird method with Hartung-Knapp adjustment. Effect sizes were expressed as odds ratios (ORs) with 95% confidence intervals (CIs). Heterogeneity was quantified using I2 statistics, and publication bias was assessed via Egger's regression test.

RESULTS: Twelve studies (8 retrospective cohort, 2 case-control, 1 prospective cohort, 1 cohort with external validation; NOS range: 6-8) comprising 4,406 children (1,123 PB cases) were included, all originating from China. A total of 38 effect sizes across 8 risk factor categories were extracted; all were multivariate-adjusted ORs. Risk factors significantly associated with PB included: lactate dehydrogenase (LDH) elevation (k=4, OR =4.06, 95% CI: 2.69-6.11, P=0.002), prolonged fever duration (k=4, OR =3.70, 95% CI: 1.12-12.26, P=0.040), D-dimer elevation (k=3, OR =2.63, 95% CI: 2.01-3.43, P=0.004), pleural effusion (k=4, OR =2.46, 95% CI: 1.55-3.91, P=0.009), atelectasis (k=4, OR =2.32, 95% CI: 1.61-3.34, P=0.005), and consolidation involving ≥2/3 lung lobe (k=2, OR =1.79, 95% CI: 1.36-2.37, P=0.02). Radiological risk factors and LDH demonstrated consistently low heterogeneity (I2=0%). One study reporting LDH as a continuous per-unit OR was excluded from the LDH pooled analysis due to scale incompatibility with dichotomized ORs. Substantial heterogeneity was observed for procalcitonin (PCT) (I2=77.8%) and fever duration (I2=47.5%).

CONCLUSIONS: Elevated LDH, prolonged fever duration, D-dimer elevation, and specific radiological features (pleural effusion, atelectasis, consolidation) are significantly associated with increased risk of PB in pediatric SMPP. These risk factors may inform early clinical risk stratification and guide decision-making regarding bronchoscopic intervention. However, their predictive accuracy requires formal evaluation using discrimination metrics. Future prospective multicenter studies are warranted to develop and validate clinical prediction models incorporating these factors.