Time-resolved Immunofluorometric Assay of Trypsin-1 Complexed with α1-Antitrypsin in Serum: Increased Immunoreactivity in Patients with Biliary Tract Cancer

Abstract

Increased serum concentrations of trypsin immunoreactivity occur in patients with biliary tract cancer. To characterize this trypsin, we developed a sensitive time-resolved immunofluorometric assay for trypsin-1 complexed with alpha(1)-antitrypsin (AAT) and studied the concentrations of this complex in sera from healthy individuals (n = 130) and patients with benign biliary disease (n = 32), biliary tract cancer (n = 17), pancreatic cancer (n = 27), and hepatocellular cancer (n = 12). We used a trypsin-1-specific monoclonal antibody on the solid phase and a europium-labeled polyclonal antibody to AAT as tracer. The detection limit was 0.42 microgram/L. The validity of the trypsin-1-AAT test for detection of biliary tract cancer was compared with trypsin-2-AAT and CA19-9. Increased concentrations of trypsin-1-AAT (>33 microgram/L) were found in 76% of patients with biliary tract cancer, and the concentrations were significantly higher than in those with benign biliary disease (P <0. 0001). The median concentration of trypsin-1-AAT in serum from patients with biliary tract cancer was 3.7-fold higher than in healthy controls, 2.6-fold higher than in patients with benign biliary tract disease, 1.7-fold higher than in patients with pancreatic cancer, and 2.0-fold higher than in patients with hepatocellular cancer. Of the markers studied, trypsin-1-AAT had the largest area (0.83) under the receiver operating curve in differentiating biliary tract cancer from benign biliary tract disease. Our results suggest that trypsin-1-AAT is a new potential marker for biliary tract cancer.