Determination of oxidative stress parameters and copeptin levels in COVID-19 according to the clinical course

COVID-19 disease, was emerged by the end of 2019 causing a pandemic and affecting different aspects of life. This disease, which has a wide range of effects ranging from health to education and even the economy, has caused various health problems to be observed in many people not only during the infection but even after the infection. Several studies reported the critical role of oxidative stress and inflammation in the pathophysiology of the disease. Copeptin, a novel biomarker, can play an important role in predicting the disease outcome in stress-induced diseases. The aim of this study is to investigate the relationship of clinical severity of COVID-19 with oxidative stress, inflammation and copeptin levels. In addition, the study parameters were statistically evaluated as prognostic biomarkers that can be used in classifying the patients according to the clinical severity of COVID-19. Patients with positive RT-PCR results for SARS-CoV-2 were divided into severe and mild groups. Healthy individuals with neither past COVID-19 infection nor vaccination were included in the study as the control group. While the severe group consisted of patients hospitalized in the intensive care unit, the mild group consisted of those who had never been hospitalized due to infection. Oxidative stress was evaluated by serum Malondialdehyde (MDA) and 4-Hydroxynonenal (4-HNE) ELISA tests. For the antioxidant capacity, serum Melatonin (MT) ELISA test was carried out. Copeptin (CPP) ELISA test was used to investigate serum copeptin levels among the study individuals. Finally, for evaluating inflammation, serum Interleukin-6 (IL-6) ELISA was performed. Our results showed that MDA and HNE-4 levels were lower in the severe group compared to mild and control groups. Additionally, IL-6 levels were significantly different between the study groups. Also, vitamin D levels showed a statistically significant difference between the study groups, where patient group was characterized by lower vitamin D levels compared to the control group. However, MT levels did not show any significant difference between the study groups. It was determined that the CPP level was significantly lower in the patient group compared to the control group. In addition, our study showed that there was a statistically significant difference between the study groups in terms of CRP and ferritin, which suggests the both parameters may be useful as prognostic markers to classify COVID-19 patients according to the disease severity. However, the fact that the levels of MDA and 4-HNE were observed to be lower among the severe group, suggests that MDA and 4-HNE adducts may have been formed, leading to false estimation of oxidative stress in the severe group. Additionally, the lower levels of MDA and 4-HNE among the treated group compared to the untreated group suggested that more comprehensive studies should be conducted regarding the effect of corticosteroid treatments on oxidative stress parameters. Keywords: COVID-19, Oxidative Stress, Inflammation, Copeptin, Antioxidant