Secretin-Pancreozymin test

Examination of the exocrine function of the pancreas is focused on determining pancreatic insufficiency, in chronic pancreatitis. The so-called „gold standard“ is a direct examination, where we perform an analysis of duodenal content after stimulation with enterohormones. It is a test whose results clearly provide the highest specificity and sensitivity, but the test is invasive, demanding for the patient, and requires a demanding laboratory analysis of duodenal content.

Two hormones, secretin and cholecystokinin, are involved in the stimulation of the pancreas. Secretin stimulates the secretion of pancreatic juice and bicarbonate production, cholecystokinin stimulates the secretion of digestive enzymes. The secretion test, therefore, allows the evaluation of only the volume of pancreatic secretion and bicarbonate concentration, to evaluate the secretion of digestive enzymes it is necessary to use combined stimulations, i.e. secretin-cholecystokinin test (PZS test; cholecystokinin = pancreozymin). Both cholecystokinin and cerulein can be used for stimulation. The secretory-cholecystokinin test is performed in many modifications, which differ in the amount of stimulating hormones, in the form of administration (i.v., an infusion), administration of an internal marker for volume correction and in the method of duodenal juice analysis.

Test Procedure
The patient arrives on an empty stomach and a serum sample is taken. Under X-ray control, a gastric tube is inserted first (used to pump gastric juice and prevent contamination of the duodenal contents) and then a second tube is inserted into the duodenum. The presence of bile in the aspirate and alkaline pH is also a control for a proper introduction. After pumping out the first fraction (fasting sample for the determination of basal values), stimulation with cholecystokinin (usually 1 IU/kg body weight i.v.) is given i.v. and duodenal juice is taken – 20 minutes. This is followed by secretin stimulation (most often 1 IU/kg body weight is given) and the other 3 fractions are pumped out after 20 minutes. Laboratory processing includes volume measurement, pH, determination, evaluation of the so-called icteric index according to the color scale, determination of HCO3-, and the activities of pancreatic enzymes &alpha;-amylase, lipase, and trypsin by conventional enzymatic methods.

The clinical significance
The secretion-cholecystokinin test provides the most accurate of all available tests on pancreas secretion ratios. Despite its non-standard nature, it is considered the „gold standard“ of pancreatic function tests to assess pancreatic insufficiency. Normal values ​​depend on the method of stimulation, collection and analysis of duodenal content. The stated values ​​are one of the variants.
 * Secretin-stimulated secretion volume 165–536 ml/hour
 * HCO3- concentration 9.8–39.7 mmol/hour
 * Trypsin activity 9.3–171 U/20 minutes
 * Amylase activity 34–204 U/20 minutes.

In some literature, we can find a variant – the so-called Lundh test, where the stimulation of the pancreas is performed with a standardized Lundh's meal. Recent studies combine endoscopy, cholecystokinin or secretin stimulation, and analysis of lipase, bicarbonate, and other enzymes in pancreatic juice taken during endoscopy, or recommend the determination of other markers, such as zinc, which is a more stable analyte than pancreatic enzymes. The tested variant of the direct test is also MRCP examination after secretin stimulation.