How does the secretin (secretin) test assess for chronic pancreatitis?

From the Guidelines

The secretin test is a valuable tool for assessing chronic pancreatitis by measuring pancreatic exocrine function after stimulation with the hormone secretin, and it remains useful in cases where the diagnosis is uncertain despite normal imaging findings. The test involves administering secretin intravenously, which normally stimulates the pancreas to secrete bicarbonate-rich fluid, and then collecting duodenal fluid to measure bicarbonate concentration. In chronic pancreatitis, the damaged pancreas produces less bicarbonate in response to secretin stimulation, with a peak bicarbonate concentration below 80 mEq/L considered abnormal and suggestive of pancreatic exocrine insufficiency consistent with chronic pancreatitis 1.

The secretin test works by targeting pancreatic ductal cells, which are responsible for bicarbonate secretion, and this function becomes impaired early in the disease process as acinar cells are progressively destroyed by inflammation and fibrosis. While imaging techniques, such as ultrasound, computerized tomography (CT), endoscopic retrograde cholangiopancreatography (ERCP), and magnetic resonance cholangiopancreatography (MRCP), have become the primary methods for diagnosing chronic pancreatitis, the secretin test remains useful in certain cases, particularly when structural changes may not yet be visible on imaging studies 1.

Some key points to consider when using the secretin test include:

• The test is highly specific and sensitive for detecting chronic pancreatitis
• It is particularly useful for detecting early or mild chronic pancreatitis
• Imaging techniques, such as ERCP and MRCP, have a high sensitivity for detecting pancreatic disease, but the secretin test can provide additional diagnostic information in certain cases
• The test involves administering secretin intravenously and collecting duodenal fluid to measure bicarbonate concentration, with a peak bicarbonate concentration below 80 mEq/L considered abnormal. According to recent guidelines, exocrine pancreatic insufficiency (EPI) should be suspected in patients with high-risk clinical conditions, such as chronic pancreatitis 1.

In terms of diagnosis and management, EPI should be considered in patients with moderate-risk clinical conditions, and the fecal elastase test is the most appropriate initial test 1. The secretin test can provide valuable information for diagnosing chronic pancreatitis, and it should be considered as part of a comprehensive diagnostic approach, particularly in cases where the diagnosis is uncertain despite normal imaging findings.

From the FDA Drug Label

When injected intravenously, sincalide stimulates gallbladder contraction and reduction in size. The evacuation of bile that results is similar to that which occurs physiologically in response to endogenous cholecystokinin. Sincalide also stimulates pancreatic secretion and intestinal motility causing pyloric contraction and slows gastric emptying Concurrent administration of sincalide with secretin increases both the volume of pancreatic secretion and the out-put of bicarbonate and enzymes. This combined effect of secretin and sincalide permits the assessment of specific pancreatic function through measurement and analysis of the duodenal aspirate.

The secretin test assesses for chronic pancreatitis by measuring the pancreatic secretion and output of bicarbonate and enzymes in response to concurrent administration of secretin and sincalide. The test involves analyzing the duodenal aspirate to evaluate specific pancreatic function 2.

• The test stimulates pancreatic secretion and measures the response.
• It assesses the output of bicarbonate and enzymes to evaluate pancreatic function.
• The combined effect of secretin and sincalide allows for the measurement and analysis of the duodenal aspirate.

From the Research

Secretin Test for Chronic Pancreatitis

The secretin test is used to assess pancreatic function and diagnose chronic pancreatitis. Here are the key points about the test:

• The test involves administering secretin intravenously and collecting duodenal juice to measure bicarbonate concentration 3.
• A bicarbonate concentration greater than 80 mmol/L in any of the samples is considered a normal result 3.
• The secretin endoscopic pancreatic function test (ePFT) has demonstrated good sensitivity and specificity compared with various reference standards, including endoscopic ultrasound and surgical histology 3.
• The test can be performed during upper endoscopy and is considered a rapid and easy method to assess pancreatic function 4, 5.

Diagnostic Accuracy

The diagnostic accuracy of the secretin test for chronic pancreatitis is as follows:

• The overall accuracy of the endoscopic secretin test was 79%, with positive and negative predictive values of 73% and 85%, respectively 5.
• The test was able to discriminate between patients with chronic pancreatitis and those with normal pancreas, with a significant difference in lipolytic concentration 5.
• The peak bicarbonate concentration had superior discrimination for chronic pancreatitis, with an area under the curve (AUC) of 0.738 6.
• The addition of enzyme concentration measurement did not improve discrimination compared with peak bicarbonate alone 6.

Prediction of Disease Progression

The secretin test can also predict the progression of minimal-change chronic pancreatitis to overt chronic pancreatitis:

• Abnormal ePFT (peak bicarbonate <80 mmol) was a significant predictor of progression, with a hazard ratio (HR) of 4.7 7.
• EUS Rosemont classification "suggestive/most-consistent" was also a significant predictor of progression, with an HR of 7.3 7.
• The test can be used to predict the development of classic chronic pancreatitis structural changes over time in patients with abdominal pain of suspected pancreatic origin and nondiagnostic cross-sectional imaging 7.