AimTo study the relationship between serum myeloperoxidase (MPO), pregnancy-associated plasma protein-A (PAPP-A) and stability of carotid plaques in patients with cerebral infarction.MethodsThe study included 52 patients with cerebral infarction and with carotid plaques confirmed by high resolution MRI.Patients were classified according to the characteristic findings of plaques in MRI.Serum levels of MPO and PAPP-A were determined by ELISA.ResultsSerum levels of MPO and PAPP-A in patients of unstable plaques group and rupture plaques group were significantly enhanced compared to individuals of stable plaques group (p<0.05 or p<0.01).Serum levels of MPO in patients of unrupture plaques group were significantly enhanced compared to individuals of stable plaques group (p<0.05).Serum levels of PAPP-A in patients of rupture plaques group were significantly enhanced compared to individuals of unrupture plaques group (p<0.01).There was no significant difference in serum levels of PAPP-A between unrupture plaques group and stable plaques group.There was no significant difference in serum levels of MPO between unrupture plaques group and rupture plaques group.The level of serum MPO and PAPP-A was positively correlated with the stability of carotid plaques.ConclusionsThere was a relationship between the serum MPO, PAPP-A and the instability of carotid plaques.High serum levels of the markers may indicate that the plaques were vulnerable or ruptured.