Sodium nitrite dosing and venous plasma nitrite concentrations correlate positively with regional forearm blood flow in patients with sickle cell disease. (A) Sodium nitrite infusions, expressed as µmol/kg, correlate positively with percentage increase over baseline forearm blood flow in patients with SCD in steady state (Spearman r = 0·70, P < 0·0001). (B) The corresponding venous plasma nitrite concentrations positively correlated with the regional forearm blood flow circulation, expressed in standard units of ml/min/100 ml of forearm tissue (Spearman r = 0·51, P = 0·003). The solid lines represent the regression line, and the dashed lines the 95% confidence limits.