The Value of Interleukin-17A as a Prognostic Indicator in COVID-19 Patients

Background: SARS-CoV-2 infections (COVID-19) first occurred in Wuhan, China, in December 2019 and spread worldwide, causing significant mortality and morbidity. IL-17A may mediate numerous immunopathological effects secondary to cytokine release syndrome during SARS-CoV-2 infection. However, there has not been enough research on its effect on prognosis. Objectives: This study evaluated the predictive power of serum interleukin (IL)-17A level as a prognostic marker in COVID-19. Methods: The study included 152 patients diagnosed with COVID-19 by real-time polymerase chain reaction analysis of nasopharyngeal swab samples in the infectious diseases department and intensive care unit of our hospital between October 1 and December 31, 2020. The control group consisted of 40 asymptomatic healthcare workers who had negative RT-PCR results during routine COVID-19 screening in our hospital. Samples were collected in anticoagulant-free tubes and left at room temperature for 30 minutes. Afterward, it was centrifuged at 1000 × g for 15 minutes at 4°C per the instructions provided with the enzyme-linked immunoassay (ELISA) kit. Serum IL-17A levels were measured using the Human Interleukin 17A ELISA Kit. Results: Serum IL-17A levels were significantly higher in COVID-19 patients than in controls (P < 0.001). IL-17A levels increased significantly in association with disease severity in patients with the moderate, severe, and critical disease, with a less pronounced difference between severe and critical patients (moderate vs. severe, P < 0.001; severe vs. critical, P = 0.048). IL-17A levels at hospital admission and day 7 were significantly higher in non-surviving patients (P < 0.001). At a cut-off value of 210.25 ng/L, IL-17A at admission had a predictive power of 0.792 (P < 0.001). Compared to baseline, IL-17A values on day seven were significantly increased in non-survivors (P = 0.004) and decreased in survivors (P = 0.014). An increase of 26.17 ng/L or more on day 7 had a predictive mortality power of 0.634 (P = 0.005). Conclusions: The results of this study suggest that IL-17A, an important part of the immune system previously shown to be useful in the treatment and follow-up of COVID-19, may also help predict mortality in COVID-19 patients.