ESTABLISHMENT AND EVALUATION OF A NEW CHEMILUMINESCENT ENZYME-IMMUNOASSAY FOR CARCINOEMBRYONIC ANTIGEN ADAPTED TO THE FULLY AUTOMATED ACCESS(R) SYSTEM

We have established a new chemiluminescent enzyme immunoassay for carc inoembryonic antigen (CEA), designated ACCESS CEA, which is adapted to the fully automated ACCESS(R) immunoassay analyzer The assay is based on a one step sandwich-type method using two monoclonal antibodies, o ne of which is immobilized on micrometer-size paramagnetic particles a nd the other is conjugated to alkaline phosphatase. Ten microliters of calibrators or sera are incubated for 5 minutes at 37 degrees C with the particles and with the alkaline phosphatase conjugate. The particl es are then magnetically separated and washed to remove unbound compon ents. Time needed to obtain the first result is less than 15 minutes. The assay range was 0.04-1000 mu g/l of CEA, and the possible high-dos e hook effect was prevented at CEA concentrations up to 100 000 mu g/l in this working range. The coefficient of variation (CV) for intra-as say precision was 3.0 to 4.7%, and inter-assay CV was 3.4 to 5.6%. The sample carryover was less than 0.001%. The analytical recovery ranged from 98 to 104% and a dilution linearity was demonstrated. No interfe rence was detected in any sample with levels up to 300 mg/l for biliru bin, 12 000 mg/l for haemoglobin, 50 000 mg/l for human serum albumin, 8 500 mg/l for triacylglycerol, and 500 000 IU/l for rheumatoid facto r. The ACCESS CEA assay also showed very homogeneous reactivity with p urified CEA preparations from different tumours and could discriminate CEA from four CEA-related normal antigens tested. Serum samples (n = 362) from patients with malignant or non-malignant disease, as well as from healthy individuals, were analyzed by the ACCESS CEA assay and b y the established IMx CEA assay. The CEA values determined by the ACCE SS CEA assay were in good agreement with those determined by the IMx C EA assay, and the ACCESS CEA assay significantly increased the sensiti vity and specificity of tumour diagnosis as compared with the IMx CEA assay.