Multicenter evaluation of the Abbott IMx CA 15-3 assay

We describe a new fully automated procedure for the quantitative measurement of CA 15-3: the microparticle enzyme immunoassay (MEIA) technology developed by Abbott Labs. for the IMx automated immunoassay analyzer. The new IMx CA 15-3 test uses two mouse monoclonal antibodies, 115D8 and DF3. The test has a dynamic range to 250 kilounits/L and a minimal detectable dose of CA 15-3 < 0.2 kilounits/L. On dilution, linearity is excellent, with recoveries ranging from 94% to 101%. Studies were conducted at four sites to evaluate the performance characteristics of this assay. The intra- and interassay CVs were < 4.7% and < 5.6%, respectively, and showed a between-laboratory CV < 5.9%. Test results of the Abbott IMx CA 15-3 (y) were correlated with those obtained with the Centocor CA 15-3 RIA (x), a solid-phase heterologous RIA. Linear regression analysis on results for 1973 samples yielded: y = 0.97x - 2.09 (r = 0.9899, Sy/x = 22.2, range 1-4089 kilounits/L).