Ceruloplasmin (Cp), a copper metalloprotein in human serum has been a valuable diagnostic marker in Wilson’s disease where Cp levels tend to be low while high levels in serum were asso-ciated with myocardial infarction, neoplastic and inflammatory conditions. There is no stan-dardized reference method for Cp and current immunologic and bichromatic assays have a number of drawbacks. The method described here uses immunoaffinity chromatography to remove six of the most abundant proteins from a serum sample and high-pressure liquid chro- matography (HPLC) with a size-exclusion col-umn to separate Cp from other serum proteins and any free Cu prior to analysis of 63Cu and 65Cu by inductively-coupled plasma mass spec-trometry (ICPMS). Identification of Cp is based on retention time match of the unknown protein in the serum sample with the Cp external stan-dard and the presence of 63Cu and 65Cu at a ratio of 2.2 ± 0.1. The method accuracy, as estab-lished independently by two of the authors with a reference serum certified for Cp, is 98 to 101% and the coefficient of variation is 6.4% and 5.4%, respectively. The assay was used to analyze a total of 167 human sera for Cp from patients with myocardial infarction (MI), pulmonary em-bolism (PE), rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), other forms of ar-thritis, and a set of healthy patients as normal controls (NC). Our data show that Cp concen-trations tend to be higher in MI, RA, and SLE patients, higher in female as compared to male patients, and we did not observe a correlation between Cp concentration and patient’s age for the set of 70 patients for which we had gender and age information.
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