Evaluation of the Analytical and Clinical Performance of the Elecsys® CA 15-3 Immunoassay

Although the sensitivity and specificity of CA 15-3 in primary diagnosis of breast cancer is limited, CA 15-3 measurement has found widespread use in monitoring disease progression and response to therapy [reviewed in Ref. (1)]. A new assay for determination of CA 15-3 on Elecsys® immunoanalyzers has been introduced by Roche Diagnostics GmbH. The analytical performance of this assay was tested in an international multicenter evaluation in 11 evaluation sites, and the clinical performance was judged in 4 of these laboratories. The results are described in this report. Elecsys CA 15-3 is a sandwich immunoassay that uses biotinylated 115D8 and ruthenylated DF3 as capture and detection antibodies, respectively, and electrochemiluminescence as the detection technology. Details of the test principle have been described previously (2). The test is standardized against the Enzymun-Test CA 15-3 (Roche Diagnostics GmbH) in the laboratories of the manufacturer. The analytical evaluation was carried out according to a standardized protocol of the European Committee for Clinical Laboratory Standards (3). The results of within-run imprecision (21 replicates per analysis) and between-day imprecision (1 replicate analyzed on 21 different days) studies are available as a data supplement at Clinical Chemistry Online (http://www.clinchem.org/content/vol47/issue12). The medians of the within-run and between-day CVs were 2.5–3.8% and 5.0–5.9%, respectively, at all concentrations tested (8.4–251.7 kilounits/L) for human sera and control sera. Confirmation of target values assigned to control sera was tested in an interlaboratory survey and was 97% for PreciControl Tumor Marker Level 1 (18.4 kilounits/L) and 96% for Level 2 (58.6 kilounits/L). The medians of all participants of an interlaboratory survey of the German Society for Clinical Chemistry were confirmed for each of the two control samples used (11.8 and 16.8 kilounits/L) by 99% (on the basis of the medians of all participants in the Elecsys study); thereby demonstrating the excellent agreement …