In addition, in a different study, MPO did not show significant difference between the control (24.2 ± 5.7 μg/L) and SA groups (26.3 ± 4.8 μg/L), but plasma MPO levels in patients with ACS (93.6 ± 20.3 μg/L) were significantly higher than in patients with stable angina and the healthy control subjects (P < 0.05) [44]. Here, MPO is linked to angina pectoris.