Methods for characterizing the near term risk of experiencing a major adverse cardiac event in a patient presenting with chest pain are provided. In one embodiment the method comprises determining the level of myeloperoxidase (MPO) activity in a bodily sample obtained from the patient. In another embodiment, the method comprises determining the level of MPO mass in a bodily sample obtained from the patient. In another embodiment, the method comprises determining the level of one or more select MPO-generated oxidation products in a bodily sample obtained from the patient. The select MPO-generated oxidation products are dityrosine, nitrotyrosine, chlorotyrosine, methionine sulphoxide or an MPO-generated lipid peroxidation product. Levels of MPO activity, MPO mass, or the select MPO-generated oxidation product in bodily samples from the test subject are then compared to a control value that is derived from measurements of MPO activity, MPO mass, or the select MPO-generated oxidation product in comparable bodily samples obtained from control population. Such comparison can also be used to determine treatment of the patient immediately at presentation in the emergency room.