Patients infected by SARS-CoV-2 can develop interstitial pneumonia, requiring hospitalisation or mechanical ventilation. Increased levels of inflammatory biomarkers are associated with development of acute respiratory distress syndrome (ARDS). The aim of the present study was to determine which cytokines are associated with respiratory insufficiency in patients hospitalised for COVID-19.
Patients and methods
Data on 67 consecutive patients were collected between March 8 and March 30, 2020. PaO2/FiO2 ratio (P/F) was calculated at hospital admission. The following cytokines were analysed: interleukin (IL)-6, IL-1α, IL-18, tumour necrosis factor (TNF)-β, macrophage colony-stimulating factor (M-CSF), macrophage migration inhibitory factor (MIF), soluble IL-2 receptor alpha (sIL-2Rα; CD25), IL-12β, IL-3, interferon (IFN) α2a, monokine induced by gamma interferon (MIG), monocyte-chemotactic protein 3 (MCP3) and hepatocyte growth factor (HGF).
P/F lower than 300 was recorded in 22 out of 67 patients (32.8%). P/F strongly correlated with IL-6 (r = –0.62, P <0.0001), M-CSF (r = –0.63, P <0.0001), sIL-2Rα (r = –0.54, P <0.0001), and HGF (r = –0.53, P <0.0001). ROC curve analyses for IL-6 (AUC 0.83, 95% CI 0.73–0.93, P <0.0001), M-CSF (AUC 0.87, 95% CI 0.79–0.96, P < 0.0001), HGF (AUC 0.81, 95% CI 0.70–0.93, P < 0.0001), and sIL-2Rα (AUC 0.80, 95% CI, 0.69–0.90, P <0.0001) showed that these four soluble factors were highly significant. All four soluble factors correlated with LDH, white blood cell count, neutrophil count, lymphocyte count, and CRP.
IL-6, M-CSF, sIL-2Rα, and HGF are possibly involved in the main biological processes of severe COVID-19, mirroring the level of systemic hyperinflammatory state, the level of lung inflammation, and the severity of organ damage.