Correlation between serum surfactant protein-D level with respiratory compliance and acute respiratory distress syndrome in critically ill COVID-19 Patients: A retrospective observational study

BACKGROUND: Acute respiratory distress syndrome (ARDS) is one of the manifestations of severe coronavirus disease 2019 (COVID-19) with low respiratory compliance and poor oxygenation as main characteristics and mortality rate of 50%–94%. Surfactants, including surfactant protein D (SP-D), have a role in maintaining respiratory compliance. This study aimed to analyze the relationship between serum SP-D levels with respiratory compliance and ARDS in patients with critically ill COVID-19 pneumonia. METHODS: This study was a cross-sectional study. Subjects were adult reverse transcription–polymerase chain reaction-confirmed COVID-19 patients who had ARDS treated with invasive mechanical ventilation. All data were obtained from medical records. Statistical analysis was done using Spearman test, Mann–Whitney test, and receiver operating characteristic curve. RESULTS: Serum level of SP-D was significantly correlated with static respiratory compliance (P = 0.009; correlation coefficient [rs] = 0.467). Serum SP-D levels correlated with ARDS severity (P < 0.001). SP-D levels had a very strong diagnostic value for ARDS severity, with an optimal cutoff value of 44.24 ng/mL (sensitivity 92.3%; specificity 94.1%). ARDS severity also correlated significantly with respiratory compliance (P = 0.005; correlation coefficient 0.496). CONCLUSION: Higher serum SP-D levels were associated with lower respiratory compliance, ARDS severity, and may be utilized diagnostically to identify patients with severe ARDS.