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 (R) GI Monitor assay on the UniCel (R) Dxl 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(R) GI Monitor assay (Beckman Coulter) was evaluated on the
UniCel(R) Dxl 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% (SD+7.2%). 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
(R = 0.959, slope = 1.004, intercept +0.17). GI Monitor serum
levels were low in healthy individuals (n = 267, median = 6.0 kU/L,
95th percentile = 23.1 kU/L), higher in individuals with various
benign diseases (n = 550, medians = 5.8-13.4 kU/L, 95th percentiles
= 30.1-195.5 kU/L) and even higher in individuals suffering from
various cancers (n = 995, medians = 8.4-233.8 kU/L, 95th
percentiles = 53.7-13,902 kU/L). Optimal diagnostic accuracy for
cancer detection against the relevant benign control group by the
GI Monitor was found for pancreatic cancer {[}area under the curve
(AUC) 0.83]. Results for the reference CA19-9 assay were comparable
(AUC 0.85). Conclusions: The Access(R) 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.