Surfactant derived protein type B: a new biomarker linked to respiratory failure and lung damage in mild to moderate SARS-CoV-2 pneumonia

Background The COVID-19 pandemic has led to significant concern due to its impact on human health, particularly through pneumonia-induced lung damage. Surfactant proteins A and D (SP-A and SP-D) are implicated in COVID-19 lung damage, but the role of surfactant protein B (SP-B) remains unclear.

Methods We conducted a single-center prospective observational study involving 73 hospitalised COVID-19 pneumonia patients. SP-B levels were measured within 48 h of admission, alongside SP-A and SP-D in a subset. Clinical data were collected, and follow-up visits were conducted after 6 months.

Results At hospitalisation, circulating immature SP-B levels measured in 73 patients (26.31 AU [14.27–41.31]), correlated significantly with lung involvement (r=0.447, p<0.001) and oxygen support requirement (p=0.005). SP-B levels did not predict mechanical ventilation or ICU admission. SP-B decreased significantly (p<0.001) from 25.53 AU [14.36–41.46] at the acute hospitalisation to 12.73 AU [9.12–20.23] at 6 months follow up, unlike SP-A and SP-D that did not change significantly. Immature SP-B (but not SP-A and SP-D) confirmed to be significantly associated with the need of oxygen support (n=26, 58%) during the hospitalisation (p<0.05).

Conclusion Immature SP-B emerges as a potential biomarker for COVID-19 pneumonia severity and prognosis. Its dynamic changes suggest utility in monitoring disease progression and long-term outcomes, despite limitations in predicting hard endpoints. Larger studies are needed to validate these findings and understand the underlying mechanisms of surfactant protein dysregulation in COVID-19 pathogenesis.