Comparison of the performance of three cancer antigen (CA) 15-3 immunoassays

Introduction: In the present study we investigated the performance, precision, and recovery of three different automated methods in determining cancer antigen (CA) 15-3 levels.Methods: Serum samples were obtained from 60 hospitalized female patients. As controls, commercially available samples were used. Cancer antigen (CA) 15-3 levels were measured using ARCHITECT CA 15-3, Elecsys® CA 15-3, and Vitros CA 15-3 immunoassays. A comparison of the results between the three methods was conducted, and the precision and recovery were analyzed.Results: Coefficient of variations (CVs), determined with low- and high-level-CA 15-3 control samples, and reproducibility values were: 2.56-2.80% and 3.10-4. 20% for ARCHITECT i2000SR immunoassay analyzer; 3.50-5.55% and 4.88-6.47% for Cobas E 601 analyzer; 3.30-4.0% and 4.30-4.80% for VITROS 5600 Integrated System, respectively. The percent recoveries were 95-98% for Elecsys® CA 15-3 assay, 93-105% for Vitros CA 15-3 assay, and 92-95% for ARCHITECT CA 15-3 assay. Method comparison results demonstrated correlation coefficient (r) in range from 0.994 to 1. The average CA 15-3 concentrations measured by Vitros, ARCHITECT, and Elecsys® were 157.24 +/- 329.75 U/mL, 100.91 +/-213.75 U/mL, and 80.93 +/- 173.29 U/mL, respectively.Conclusions: Tumor marker CA 15-3 in individual patients should be monitored using the same immunoassay method, reagents, and analyzer. Different immunoassays tested on different analyzers, often show large discrepancies in reported values for individual patients. Different immunoassay technologies quantify analytes of clinical interest using monoclonal or polyclonal antibodies. Thus, the usage of antibodies with different specificities could explain the differences in CA 15-3 serum values between different methods.