What is the purpose and procedure of the secretin stimulation test (SST) in diagnosing conditions like Zollinger-Ellison syndrome and pancreatic insufficiency?

From the Research

The secretin stimulation test (SST) is a crucial diagnostic tool for evaluating pancreatic function and diagnosing conditions like Zollinger-Ellison syndrome and pancreatic insufficiency, with the most recent and highest quality study 1 guiding its use. The test works by measuring the pancreatic response to secretin, a hormone that normally stimulates pancreatic secretions. During the procedure, a baseline blood sample is first collected to measure fasting gastrin or bicarbonate levels. Then, synthetic secretin (typically 0.2-0.4 μg/kg) is administered intravenously as a bolus. Following administration, multiple blood samples are collected at timed intervals (usually at 5,10,15, and 30 minutes) to measure the response. In Zollinger-Ellison syndrome, secretin causes an abnormal increase in gastrin levels (typically a rise of >200 pg/mL above baseline), while in pancreatic insufficiency, there is a diminished bicarbonate response in duodenal fluid (peak concentration <80 mEq/L). Some key points to consider when performing the SST include:

• Patients should fast for 12 hours before the test and discontinue medications that affect gastric acid secretion (like proton pump inhibitors) for at least 7 days prior 1.
• The test is relatively safe with minimal side effects, which may include temporary abdominal discomfort, nausea, or flushing.
• The SST is valuable because it provides objective measurements of pancreatic function that help differentiate between various gastrointestinal disorders when clinical symptoms overlap.
• A gastrin increase of >100 ng/l is considered the most sensitive and specific criterion for a positive test, as shown in a study comparing different dosages of secretin 2.
• The 0.26 microg/kg secretin stimulation test has been found to have the best diagnostic efficacy for Zollinger-Ellison syndrome 2.
• Recent updates on Zollinger-Ellison syndrome and gastrinoma diagnosis and management emphasize the importance of the secretin stimulation test in differentiating ZES from other hypergastrinemic states 1.