Sensitivity and specificity of radioimmunoassay of serum trypsin-like immunoreactivity for the diagnosis of canine exocrine pancreatic insufficiency.

Concentrations of serum trypsin-like immunoreactivity (TLI) measured by radioimmunoassay were low (less than 1.9 micrograms/L) in 25 dogs with exocrine pancreatic insufficiency (EPI), compared with 100 clinically normal (control) dogs (5.2 to 34.0 micrograms/L; P less than 0.001; sensitivity, 100%). Serum TLI concentrations (5.5 to 35.0 micrograms/L) in a group of 50 dogs with small intestinal disease (SID) were not significantly different from those of control dogs, values being greater than the lower limit of the control range in all cases (specificity, 100%). Results of bentiromide (N-benzoyl-L-tyrosyl-p-aminobenzoic acid [BT-PABA]) tests and fecal proteolytic activity (determined by use of an azocasein substrate) were abnormal in 21 of 22 dogs with EPI (sensitivity, 95%). Bentiromide test results were subnormal in 13 of 35 dogs with SID (specificity, 63%), whereas fecal proteolytic activity was subnormal in 7 of 34 dogs with SID (specificity, 79%). It was concluded that assay of serum TLI is a highly sensitive and specific test for the identification of dogs with EPI.