Circulating Surfactant Protein-D for Risk Stratification in Paediatric Acute Lung Infections: A Systematic Review

Area of Science:

• Pediatric Pulmonology
• Biomarkers in Infectious Disease
• Critical Care Medicine

Background:

• Surfactant protein-D (SP-D) is released into circulation upon injury to the alveolo-capillary barrier.
• Acute infectious lung diseases in children can compromise this barrier, leading to SP-D release.

Purpose of the Study:

• To synthesize evidence on the diagnostic and prognostic performance of circulating SP-D in children with acute infectious lung disease.
• To evaluate SP-D's role in differentiating disease severity and predicting outcomes in pediatric respiratory infections.

Main Methods:

• Systematic literature search of MEDLINE, Embase, and Scopus (inception-June 1, 2025) for human studies.
• Inclusion of studies on pediatric patients (<18 years) with community-acquired pneumonia (CAP), viral pneumonitis, or pediatric acute respiratory distress syndrome (PARDS).
• Narrative synthesis due to heterogeneity in assays and outcome definitions; risk of bias assessed using ROBINS-I.

Main Results:

• Five studies (n=723) reported higher admission SP-D levels in severe CAP (AUCs 0.699-0.802).
• SP-D thresholds (110-180 ng/mL) showed sensitivities of 67-85% and specificities of 45-70%.
• SP-D correlated with ventilator days (r≈0.45) and ICU stay (r≈0.44) in influenza-associated respiratory failure; each 10 ng/mL increase in SP-D associated with higher odds of severe PARDS and death (aOR 1.02).

Conclusions:

• Elevated circulating SP-D correlates with disease severity, radiographic findings, and adverse short-term outcomes in pediatric lung infections.
• SP-D shows potential as a biomarker for risk stratification in childhood pneumonia and viral lung injury.
• Assay standardization and external validation are recommended for clinical integration of SP-D into multiparametric risk algorithms.