CXCL8 and sickle cell disease: Among the patients with sickle cell disease, we observed bivariate associations of higher interleukin-6, interleukin-8, interferon-γ, tumor necrosis factor-α and RANTES concentrations with higher tricuspid regurgitation velocity, and an independent association of increased interleukin-6 concentration with elevated tricuspid regurgitation velocity.