Are Serum Interleukin 6 and Surfactant Protein D Levels Associated with the Clinical Course of COVID-19?

Lung. 2020 Oct;198(5):777-784. doi: 10.1007/s00408-020-00393-8. Epub 2020 Sep 12.


Purpose: SARS-CoV-2 (COVID-19) has infected more than 7 million people worldwide in the short time since it emerged in Wuhan, China in December 2019. The aim of this study was to investigate the relationship between serum interleukin 6 (IL-6) and surfactant protein D (SP-D) levels and the clinical course and prognosis of COVID-19.

Materials and methods: The study included a total of 108 individuals: 88 patients who were diagnosed with COVID-19 by real-time PCR of nasopharyngeal swab samples and admitted to the Atatürk University Pulmonary Diseases and the Erzurum City Hospital Infectious Diseases department between March 24 and April 15, and 20 asymptomatic healthcare workers who had negative real-time PCR results during routine COVID-19 screening in our hospital.

Results: Patients who developed macrophage activation syndrome had significantly higher IL-6 and SP-D levels at the time of admission and on day 5 of treatment compared to the other patients (IL-6: p = 0.001 for both; SP-D: p = 0.02, p = 0.04). Patients who developed acute respiratory distress syndrome had significantly higher IL-6 and SP-D levels at both time points compared to those who did not (p = 0.001 for all). Both parameters at the time of admission were also significantly higher among nonsurvivors compared to survivors (IL-6: p = 0.001, SP-D: p = 0.03).

Conclusion: In addition to IL-6, which has an important role in predicting course and planning treatment in COVID-19, SP-D may be a novel pneumoprotein that can be used in the clinical course, follow-up, and possibly in future treatments.

Keywords: Acute respiratory distress; COVID-19; Interleukin 6; Surfactant protein D.

MeSH terms

  • Betacoronavirus / isolation & purification*
  • COVID-19
  • COVID-19 Testing
  • Clinical Laboratory Techniques / methods
  • Coronavirus Infections* / blood
  • Coronavirus Infections* / diagnosis
  • Coronavirus Infections* / epidemiology
  • Female
  • Hospitalization / statistics & numerical data
  • Humans
  • Interleukin-6 / blood*
  • Male
  • Middle Aged
  • Pandemics*
  • Pneumonia, Viral* / blood
  • Pneumonia, Viral* / diagnosis
  • Pneumonia, Viral* / epidemiology
  • Predictive Value of Tests
  • Prognosis
  • Pulmonary Surfactant-Associated Protein D / blood*
  • Risk Factors
  • SARS-CoV-2
  • Turkey / epidemiology


  • Interleukin-6
  • Pulmonary Surfactant-Associated Protein D