CA-15-3 - A MULTICENTER EVALUATION OF AUTOMATED AND MANUAL TESTS

The introduction of a new and automated CA 15-3 immunoassay (IMx Abbot t) prompted us to compare the analytical performance of this new test with established tests from CIS ELSA, Sorin, and Boehringer Mannheim i n a multicentre study. CA 15-3 measurements in blood samples of breast tumour patients, comparison of intra- and inter-assay variation, dilu tion linearity, and lower limit of detection are described. The study showed improved precision for the automated over the manual test syste ms (intra-assay variation: IMx < 5%, CIS ELSA 4-9%, ES 300 < 3% and ET I Sorin > 10%; inter-assay variation: IMx less than or equal to 8%, CI S ELSA less than or equal to 19%, ES 300 less than or equal to 9% and ETI Sorin less than or equal to 27%). Results on patients' samples (n = 101 to 184) showed highly comparable results; IMx vs CIS ELSA site 1 : 0.950; IMx vs CIS ELSA site 2: r = 0.998; IMx vs ES 300: r = 0.980; IMx vs ETI Sorin: r = 0.931. Slopes of regression lines varied from 0. 666 for IMx vs ETI Sorin to 0.988 for IMx vs CIS ELSA (site 1, where h eparin plasma was used instead of serum as recommended by the manufact urer). Slopes and correlation coefficients were found to be only sligh tly dependent on assay ranges analysed by statistical procedures appli ed. Despite good correlations between methods, it is recommended that samples collected in the follow-up of disease and at higher CA 15-3 co ncentrations are analysed by the same test; a changeover to another te st is not encouraged.