Evaluation of serum complement C4 among COVID-19 patients in Khartoum state: a case control-based study [version 1; peer review: 2 approved]

Background: The complement system is made up of an abundance of unique plasma proteins that play an important role in innate immunity and inflammation, aiding in the fight against pathogenic microbes and viral diseases. The purpose of this study was to evaluate the serum complement C4 concentration in COVID-19 patients in Khartoum and compare them to healthy controls. Methods: A total of 100 samples were collected, 50 samples from COVID-19 patients who presented as cases and 50 samples from people who were evidently healthy. Overall, 33 (66%) the patient populations in the case group were not in the hospital’s intensive care unit (ICU), compared to 17 (34%) who were. The concentrations of C4 in each serum sample were calculated in milligrams per deciliter. SPSS version (20) was used to analyze the data. Results: The means level of complement C4 (mg/dL) were 37.44±18.618, 23.90±10.229 in the case group and in the control group, respectively. There was a statistically significant difference in complement C4 level between case and control (p-values ≤0.01). In addition, the mean complement C4 level in the ICU and non-ICU case groups was 25.00±17.85 and 43.85±15.712 mg/dL, respectively. There was a statistically significant variance in complement C4 level between ICU and non-ICU (p-values ≤0.01). Furthermore, the cases were divided into four age groups: 20-40, 40-60, 60-80, and over 80 years old. The one-way ANOVA test showed no statistically significant differences between age categories in complement C4 level (P = 0.735) Conclusions: The case group had a higher mean level of complement C4 than the control group, which could be understood by the stimulation of the complement cascade during the COVID-19 illness. Furthermore, the complement C4 level in severe COVID-19 patients was lower than in non-severe COVID-19.