Performance characteristics of five automated CA 19-9 assays

Serum concentrations of cancer antigen (CA) 19-9 can be useful in monitoring response to therapy in pancreatic cancer The objective of this study was to evaluate 5 automated CA 19-9 assays: ARCHITECT i2000 (Abbott Diagnostics, Abbott Park, IL), ADVIA Centaur (Bayer Diagnostics, Tarrytown, NY), UniCel DxI 800 (Beckman Coulter, Fullerton, CA), IMMULITE 2000 (Diagnostic Products, Los Angeles, CA), and Elecsys El 70 (Roche Diagnostics, Indianapolis, IN). All methods were evaluated for limit of detection, linearity, imprecision, method comparison, and reference intervals. Limit of detection results were all below 2.0 KU/L and met the manufacturers' claims. Linearity had deviation front target values that ranged from 4.5% to 26.7%. All methods showed acceptable imprecision with total coefficients of variation less than 8%. Method comparison by Passing-Bablok analysis resulted in slopes ranging from 1.00 to 2.06 and correlation coefficients of 0.85 to 0.98. Between 97.6% and 99.2% of results from healthy volunteers were less than 35 KU/L. All methods show acceptable analytic performance.