Plasma immunoreactive anionic pancreatic trypsin in cystic fibrosis

Previous data from this laboratory have shown good correlation between plasma cationic trypsin(ogen) and levels of pancreatic function in older cystic fibrosis (CF) patients with and without malabsorption. In the present study a radioimmunoassay for human anionic trypsin(ogen) has been employed in the assessment of pancreatic function in older patients with CF. Immunoreactive anionic trypsin(ogen) levels correlated poorly with pancreatic function due to an apparent elevation of this enzyme in many older CF patients with malabsorption (CF + M). When plasma from three older CF + M patients is examined for the molecular size of the apparent immunoreactive material detected, no free anionic trypsinogen is observed. Instead, a broad peak of apparent immunoreactive material appears in the gammaglobulin region. However, only free anionic trypsinogen could be detected in plasma from two CF patients without malabsorption (CF - M), who had not received pancreatic enzyme supplements. It appears possible that a human plasma immunoglobulin G (IgG) to porcine pancreatic enzyme in the CF + M patients might interfere in the assay by binding TLCK--anionic trypsin tracer. It is unclear why such an effect does not appear to occur in the cationic trypsin(ogen) assay. The results of the current study suggest that, for assessment of pancreatic insufficiency in CF, the radioimmunoassay for cationic trypsin(ogen) is more useful than the presently available radioimmunoassay for the anionic form.