Simplified method to assay total plasma peroxidase activity and ferriheme products in sickle cell anemia, with initial results in assessing clinical severity in a trial with citrulline therapy

A method using dianisidine is described to measure promptly the total plasma peroxidase (POX) activity of methemoglobin and other ferrihemes. Methemoglobin (35 mg/dL) is used as POX standard. Three-minute POX activities and total POX concentrations measured by a classic benzidine method were compared in a three-patient trial with citrulline supplementation. High POX values became progressively lower. In two of the patients, 3-minute POX activities were reduced more than total concentrations. Oral citrulline reduced harmful plasma ferriheme levels. Free ferriheme also exhibited POX activity. POX levels may be useful to judge severity in sickle cell anemia and to monitor therapeutic efficacy.