Evaluation of the relationship between surfactant protein D levels and COVID-19 clinical severity: a case-control study

Abstract

Purpose: Serum surfactant protein D (SP-D) plays roles in the body such as protection against viral infection,bacterial and fungal clearance, clearance of apoptotic cells and suppression of inflammation. This study aims toexamine the relationship between SP-D level and coronavirus disease (COVID-19) severity.Methods: 80 patients (30 with mild disease and 50 with severe/critical COVID-19), and 50 healthy volunteerswere enrolled in the study. SP-D levels were analyzed by ELISA in serum samples.Results: The median of SP-D was found to be 2.47 (1.67-7.79) ng/ml in mild disease and 5.65 (3.09-16.55) ng/ml in severe/critical disease groups, while 2.89 (10.8-6.24) ng/ml in the healthy controls. The differences in SP-Dlevels between the severe/critical disease group compared to both mild disease and control groups were foundstatistically significant (p=0.007 and 0.001, respectively). ROC analysis showed greater AUC for the serumSP-D levels of the severe/critical COVID-19 patients compared to mild COVID-19 disease patients (AUC=0,691,95% CI=0.56-0,822; p=0.004). Furthermore, SP-D levels were 86% sensitive and 51.6% specific at 2.44 ng/mllevel (p=0.004) to detect severe/critical patients.Conclusion: SP-D levels is useful for COVID-19 patients in the prediction of clinical severity and prognosis.SP-D is a valuable biomarker for predicting the clinical severity and prognosis.