Time-resolved immunofluorometric assay of trypsin-2 complexed with alpha 1-antitrypsin in serum.

We developed a sensitive time-resolved immunofluorometric assay (IFMA) for trypsin-2 complexed with alpha 1-antitrypsin (AAT). We used a trypsin-2-specific monoclonal antibody on the solid phase and a europium-labeled polyclonal antibody to AAT as tracer. The detection limit is 0.05 microgram/L and the range of linearity extends to 100 micrograms/L. We compared the clinical utility of the trypsin-2-AAT assay with that of free trypsinogen-2 and amylase in serum by studying 120 healthy subjects, 29 patients with acute pancreatitis, 11 with extrahepatic biliary obstruction, and 34 with acute abdominal disorders of extrapancreatic origin. In patients with acute pancreatitis the median concentration of trypsin-2-AAT in serum was 59-fold that in healthy controls, 42-fold that in patients with biliary obstruction, and 33-fold that in patients with acute abdominal disorders of extrapancreatic origin. These differences are greater than those for trypsinogen-2 (19-, 20-, and 28-fold, respectively) and amylase (5.4-, 6.5-, and 5.4-fold, respectively). Compared with the assays of free trypsinogen-2 and amylase, our assay of trypsin-2-AAT improved the clinical specificity for acute pancreatitis by eliminating false-positive results in our control groups. Increased concentrations of trypsin-2-AAT and trypsinogen-2 were also observed in patients with chronic renal failure undergoing dialysis.