Evaluation of interleukin-38 levels in serum of patients with coronavirus disease 2019.

Interleukin-38 (IL-38) has recently been considered as a cytokine with anti-inflammatory properties in viral respiratory infections, particularly coronavirus disease 19 (COVID-19), but the evidence has not been well elucidated. Therefore, a case-control study was conducted to determine IL-38 serum levels in 148 patients with COVID-19 (45 moderate, 55 severe, and 48 critical) and 113 controls. Results demonstrated that IL-38 levels did not show significant differences between patients and controls (68.7 [interquartile range: 62.7-75.6] vs. 67.7 [58.0-82.6] pg/ml; probability = 0.457). Similarly, patients stratified by disease severity, age group, gender, or chronic disease showed no significant differences between IL-38 levels in each stratum. Whereas, overweight/obese patients had a significantly lower median of IL-38 compared to normal-weight patients. Further, IL-38 showed significantly higher levels in the age group ≥50 years of patients with critical illness than in the age group <50 years. Female patients with severe disease also showed significantly elevated levels of IL-38 compared to male patients. In conclusion, the study indicated that serum IL-38 levels were not affected by COVID-19 infection, but the distribution of patients according to disease severity, age, gender, and body mass index may better reveal the role of IL-38 in disease pathogenesis.