Interference by Gastrografin with a spectrophotometric trypsin assay

Area of Science:

• Gastroenterology
• Biochemistry
• Diagnostic Assays

Background:

• Gastrografin is a contrast agent used in medical imaging.
• Accurate pancreatic function tests are crucial for diagnosing gastrointestinal disorders.
• Spectrophotometric assays are commonly used for enzyme determination.

Purpose of the Study:

• To investigate the potential interference of Gastrografin with spectrophotometric trypsin assays.
• To identify the mechanisms by which Gastrografin might affect assay results.
• To provide recommendations for optimizing pancreatic function testing.

Main Methods:

• Gastrografin was introduced into the intestinal tract.
• Trypsin values were determined using a spectrophotometric assay system.
• Interference was assessed by measuring absorbance at 254 nm and evaluating enzyme inhibition.
• Amylase and lipase determinations were also performed.

Main Results:

• Residual Gastrografin caused falsely low trypsin values in spectrophotometric assays.
• High absorbance of Gastrografin at 254 nm led to elevated background optical density.
• Gastrografin inhibited the esterase activity of the synthetic substrate used in the assay.
• No interference was observed with gelatin proteolysis by trypsin, amylase, or lipase determination.

Conclusions:

• Gastrografin interferes with spectrophotometric determination of trypsin.
• Avoid instilling Gastrografin before pancreatic function tests requiring trypsin measurement.
• The interference is attributed to absorbance and enzyme inhibition properties of Gastrografin.