Latex particle immunoassay of carcinoembryonic antigen.

Immunoassay by particle counting (IMPACT) was used to assay carcinoembryonic antigen. The dynamic range in serum was shown to extend from 1 to 120 ng/ml with a detection limit of 0.3 ng/ml. With a total throughput time of 52 min, the assay displayed intra- and inter-assay coefficients of variation ranging from 5.4 to 9.8%. Good specificity was obtained with the aid of monoclonal antibodies and by peptic digestion of the serum sample. The method was compared with three different RIAs and one EIA test and correlation coefficients of 0.94-0.97 were obtained. CEA levels in normal individuals (smokers and non-smokers) and in various diseases were also measured.