Background: Coronavirus disease 2019 (COVID-19) is a multisystem disease of global significance. Interleukin (IL)-6 is a soluble cytokine with a pleiotropic effect on inflammation and the immune response.
Objectives: Investigate the relationship between the interleukin 6 (IL6) rs1800795 variant and IL6 level in Turkish patients with COVID-19 disease.
Design: Prospective cohort study.
Setting: Tertiary care hospital.
Patients and methods: Real-time polymerase chain reaction (RT-PCR)-positive and/or chest computerized tomography (CT) scan-compatible COVID-19 patients were enrolled in the study. The clinical data and whole blood samples were collected from April 1, 2020, to August 1, 2020. IL6 rs1800795 genotyping was performed by the PCR-restriction fragment-length polymorphism (RFLP) method in 148 patients. Serum IL-6 concentrations were measured using the ELISA method in 89 patients. We evaluated the patients in three groups: asymptomatic, symptomatic, and intensive care unit patients.
Main outcome measures: IL6 rs1800795 genotype frequencies and serum IL-6 levels in COVID-19 patients with different clinical presentations.
Sample size: 148 cases.
Results: IL6 rs1800795 GG genotype and G allele frequency increased in PCR positive patients compared to PCR-negative patients (p ˂ 0.000). IL6 rs1800795 GC genotype and C allele frequency were lower in PCR-positive patients than in PCR-negative patients. IL6 rs1800795 GG genotype and G allele frequency were higher in asymptomatic patients than in the symptomatic and intensive care unit groups. The IL6 rs1800795 C allele frequency was lower in asymptomatic patients than in the symptomatic and intensive care unit groups. IL6 rs1800795 GG genotype and G allele frequency were higher in CT negative patients than CT positive patients, while IL6 GC genotype and C allele frequency were higher in CT positive patients than negative patients. IL6 level elevation was seen in the asymptomatic patients compared to the symptomatic and intensive care unit groups.
Conclusions: These findings suggest that IL6 rs1800795 may contribute to the susceptibility of COVID-19 in people to Turkish origin.
Limitations: Further large-scale studies in different genetic populations are needed as this is a single-center, prospective study.
Keywords: Covıd-19; interleukin 6; real-time polymerase chain reaction; variant.