ABSTRACT
Purpose Previous studies have suggested that patients with IgA nephropathy (IgAN) was associated with an increased risk of coronavirus disease 2019 (COVID-19) infection. However, the findings were inconsistent, and whether there was a causality between IgAN and COVID-19 infection remains unknown. This study was performed to estimate the casual effect between IgAN and COVID-19 infection with the implementation of bidirectional Mendelian randomization (MR) analysis.Methods Genetic summary data of IgAN was derived from a large genome-wide association study (GWAS) that consisted of 14,361 cases and 43,923 controls. The genetic data of COVID-19 comprised of three phenotypes, including hospitalization, severity and infection, which had a population more than 20 million. The methods of inverse variance weighting (IVW), MR-Egger, weight median and weighted mode were applied for causal inference in MR analysis.Results In the forward direction, the IVW’s results proved that IgAN did not have causal relationships with hospitalization COVID-19 (OR = 1.077, 95%CI: 0.953–1.217, P = 0.236), severe COVID-19 (OR = 1.059, 95%CI: 0.878–1.278, P = 0.547) and COVID-19 infection (OR = 0.973, 95%CI: 0.929–1.109, P = 0.243). Furthermore, reverse MR analysis showed no evidence of causal associations of hospitalization COVID-19 (OR = 1.017, 95%CI: 0.968–1.069, P = 0.499), severe COVID-19 (OR = 1.005, 95%CI: 0.979–1.078, P = 0.781) and COVID-19 infection (OR = 1.030, 95%CI: 0.909–1.169, P = 0.641) with the risk of IgAN.Conclusion Our study does not support a casual association of IgAN with the risk of COVID-19 infection, nor does the causality between COVID-19 infection and IgAN risk.