Surfactant protein D as a marker of persistent impairment of the lungs diffusion capacity in the long-term period in patients who had suffered from severe COVID-19

Abstract

Introduction. The long-term consequences of COVID-19 (СOrona VIrus Disease 2019) for the respiratory system represent a socially significant problem. Long-lasting respiratory symptoms and functional changes in individuals who have suffered coronavirus infection justify the need to study pathogenetic mechanisms. There is little study of epithelial biomarkers and their potential role in the development of long-term respiratory complications.Aim. Тo study the level of the circulating marker surfactant protein- D (SP-D) in patients who suffered severe COVID-19-associated lung damage at 3 and 12 months after the acute form and its relation with indicators of respiratory function.Materials and methods. The study included 70 patients who were examined at 3 and 12 months after the acute phase of COVID-19, which occurred with severe and extremely severe lung damage. Patients underwent a comprehensive study of respiratory function (spirography, bodyplethysmography and diffusion test), a 6-minute step test with quantitative assessment of shortness of breath, both during exercise and in daily life; the study also determined the serum level of surfactant protein-D.Results. The results of the study indicate that 57% of patients who have suffered severe COVID-19-associated lung damage remain persistently impaired in the diffusion capacity of the lungs throughout the year. It was found that the level of SP-D was increased in all patients 3 months after the acute phase of the disease, but in the group with reduced DLco this level was significantly higher after 3 and 12 months (469 ng/ml and 295 ng/ml, respectively).Conclusion. Persistent impairments in the diffusion capacity of the lungs in some patients persist a year after suffering a severe form of COVID-19. Elevated SP-D levels have been found to be associated with decreased lung diffusion capacity. Thus, SP-D can be considered as a potential biomarker of lung injury severity in the long-term period of COVID-19.