A comparison of four immunometric assays for myeloperoxidase using luminescent and colorimetric signal detection

This communication presents four different assay systems for the determination of myeloperoxidase in body fluids. One is based on conventional chemiluminescence, two on luminescence-amplified enzyme measurement using either spiroadamantane-1,2-dioxetanes with alkaline phosphatase or luminol/peroxidase/4-iodophenol coupled with a peroxidase label. The assays covered the range 0-600 micrograms/l peroxidase. Established reference range for EDTA plasma from healthy volunteers gave an upper limit of 250 micrograms/l (95% confidence limits). Intra-assay coefficients of variation were less than 5% for all assays, as seen in compound precision profiles. Inter-assay variation was less than 10% throughout the whole concentration range. Kinetic curves for the light production were performed over a 2 hour period for the enhanced luminescence assays. Dynamic ranges of these assays were compared with the conventional colorimetric assay using 4-nitrophenyl phosphate--alkaline phosphatase. The assay was standardized using a commercially available myeloperoxidase preparation with defined enzymatic activity. The protein content was estimated and the laboratory standard compared and calibrated in mass units.