Alternative antibody for the detection of CA19-9 antigen: a European multicenter study for the evaluation of the analytical and clinical performance of the Access GI Monitor assay on the UniCel DxI 800 Immunoassay System

Background: Gastrointestinal cancer antigen CA19-9 is known as a valuable marker for the management of patients with pancreatic cancer. Methods: The analytical and clinical performance of the Access GI Monitor assay (Beckman Coulter) was evaluated on the UniCel DxI 800 Immunoassay System at five different European sites and compared with a reference method, defined as CA19-9 on the Elecsys System (Roche Diagnostics). Results: Total imprecision (%CV) of the GI Monitor ranged between 3.4% and 7.7%, and inter-laboratory reproducibility between 3.6% and 4.0%. Linearity upon dilution showed a mean recovery of 97.4% (SDq7.2%). Endogenous interferents had no influence on GI Monitor levels (mean recoveries: hemoglobin 103%, bilirubin 106%, triglycerides 106%). There was no high-dose hook effect up to 115,000 kU/L. Clinical performance investigated in sera from 1811 individuals showed a good correlation between the Access GI Monitor and Elecsys CA19-9 (Rs0.959, slopes1.004, interceptsq0.17). GI Monitor serum levels were low in healthy individuals (ns267, medians6.0 kU/L, 95th percentiles23.1 kU/L), higher *Corresponding author: Dr. med. Petra Stieber, Institut für Klinische Chemie, Klinikum der Universität München, Marchioninistr. 15, 81366 Munich, Germany Phone: q49-89-7095-3115, Fax: q49-89-7095-6298, E-mail: [email protected] Received July 19, 2007; accepted October 4, 2007 in individuals with various benign diseases (ns550, medianss5.8–13.4 kU/L, 95th percentiless30.1–195.5 kU/L) and even higher in individuals suffering from various cancers (ns995, medianss8.4–233.8 kU/L, 95th percentiless53.7–13,902 kU/L). Optimal diagnostic accuracy for cancer detection against the relevant benign control group by the GI Monitor was found for pancreatic cancer warea under the curve (AUC) 0.83x. Results for the reference CA19-9 assay were comparable (AUC 0.85). Conclusions: The Access GI Monitor provides very good methodological characteristics and demonstrates an excellent analytical and clinical correlation with the Elecsys CA19-9. The GI Monitor shows the best diagnostic accuracy in pancreatic cancer. Our results also suggest a clinical value of the GI Monitor in other cancers. Clin Chem Lab Med 2008;46:600–11.