NE levels in the plasma of patients with IM. The levels of NE in the plasma of healthy subjects (n = 19), patients with PV (n = 15), and patients with IM (n = 32) were assayed by ELISA. Each point represents the mean of the concentration of NE in each individual plasma sample assayed in duplicate. The bars represent the mean of each sample group. The levels of NE in the plasma of healthy control subjects were significantly less than that of both patients with IM (P < .001) and patients with PV (P < .01). There was no significant difference between the levels of NE in plasma from patients with IM and PV (P > .05).