What is the mechanism of the secretin (secretin hormone) stimulation test?

From the Guidelines

The secretin test is a diagnostic procedure used to evaluate pancreatic function by measuring the pancreas's response to the hormone secretin, and it works by stimulating the pancreas to produce bicarbonate-rich pancreatic juice, with bicarbonate concentration in the duodenal fluid increasing significantly after secretin administration, typically exceeding 80 mEq/L in healthy individuals 1.

How the Secretin Test Works

The test involves collecting a baseline duodenal fluid sample, then administering synthetic secretin (typically 0.2-0.4 μg/kg) intravenously, followed by collecting multiple duodenal fluid samples over 60-80 minutes through a tube placed in the duodenum.

• The test measures bicarbonate concentration, fluid volume, and enzyme output, providing comprehensive information about pancreatic function.
• Lower bicarbonate levels suggest pancreatic exocrine insufficiency, as seen in chronic pancreatitis or cystic fibrosis.
• The secretin test has been largely replaced by imaging techniques like MRCP for many pancreatic conditions, but it remains valuable for diagnosing early chronic pancreatitis and evaluating pancreatic exocrine function when other tests are inconclusive 1.

Clinical Applications

• The secretin test is used to diagnose and evaluate pancreatic exocrine insufficiency, particularly in cases where other tests are negative or equivocal.
• It is also used to assess pancreatic function in patients with suspected chronic pancreatitis or other pancreatic disorders.
• The test can help identify patients who may benefit from pancreatic enzyme replacement therapy or other treatments to manage their condition 1.

Limitations and Alternatives

• The secretin test is an invasive procedure that requires specialized equipment and expertise.
• It has been largely replaced by non-invasive imaging techniques like MRCP, which are more convenient and less risky for patients.
• However, the secretin test remains a valuable diagnostic tool in certain situations, particularly when other tests are inconclusive or unavailable 1.

From the FDA Drug Label

To Stimulate Pancreatic Secretion in Combination with Secretin 30 minutes after initiation of secretin for injection, administer 0.02 mcg/kg diluted in 30 mL of 0. 9% Sodium Chloride Injection USP and infused over 30 minutes at a rate of 1 mL per minute.

The secretin test works by stimulating pancreatic secretion in combination with sincalide. The test involves administering secretin for injection, followed by sincalide 30 minutes later. The sincalide is administered as an intravenous infusion over 30 minutes. The test is used to obtain a duodenal aspirate for analysis of enzyme activity, composition, and cytology 2.

From the Research

How the Secretin Test Works

• The secretin test is a pancreatic function test that measures the exocrine function of the pancreas 3, 4, 5, 6.
• The test involves the administration of intravenous secretin, which stimulates the pancreas to secrete bicarbonate and enzymes into the duodenum 3, 4, 5, 6.
• The duodenal secretions are then collected and analyzed for bicarbonate concentration, which is used to assess pancreatic exocrine function 3, 4, 5, 6.
• A normal result is typically defined as a bicarbonate concentration greater than 80 mmol/L in any of the collected samples 3.

Procedure and Interpretation

• The secretin test can be performed using an endoscopic approach, where duodenal aspirates are collected through the suction channel of the endoscope 3, 4, 5, 6.
• The test can also be performed using a modified scoring system, which takes into account bicarbonate and fecal elastase 1 (FE1) levels 6.
• The diagnostic accuracy of the secretin test has been shown to be high, with positive and negative predictive values of 100% and 80%, respectively 6.
• The test has been compared to other diagnostic methods, such as endoscopic ultrasound (EUS) and surgical histology, and has been shown to be a valuable tool in the diagnosis of chronic pancreatitis 3, 4, 5.

Variations and Applications

• The secretin test can be combined with other stimuli, such as cholecystokinin (CCK), to evaluate pancreatic function 5.
• The test has been used to diagnose early-stage chronic pancreatitis, and has been shown to be superior to other diagnostic methods, such as fecal elastase 1 (FE1) testing 6.
• Secretin-enhanced magnetic resonance cholangiopancreatography (MRCP) has also been used to diagnose early-stage chronic pancreatitis, and has been shown to be a valuable diagnostic tool 7.