CD19 and atrial fibrillation: According to the IVW method, the expression level of CD19 on B cells, absolute CD4−CD8− T cell counts, and relative CD8+ T cell count levels were positively correlated with AF, with odds ratio (OR), 95% confidence interval (95% CI), and P value of (OR: 1.0379, 95% CI: 1.0075–1.0697; P = .0140), (OR: 1.0529, 95% CI: 1.0132–1.0943; P = .0086), (OR: 1.0316, 95% CI: 1.0047–1.0593; P = .0211).