Pancreatic Polypeptide

Serum, frozen

0.5 mL

0.3 mL (Note: This volume does not allow for repeat testing.)

Red-top tube or gel-barrier tube

Patients should fast for 10 hours prior to specimen collection. No radioisotopes should be administered during the 24 hours prior to specimen collection.

Measurement of pancreatic polypeptide in serum

This test was developed and its performance characteristics determined by Labcorp. It has not been cleared or approved by the Food and Drug Administration.

Elevated results can occur 30 to 90 minutes after a meal and after exercise.^1,2 Can be elevated in patients with uncontrolled diabetes mellitus.

Decreased results can be seen in patients treated with atropine or somatostatin.^1,2 Can be decreased in patients with hyperglycemia, chronic pancreatitis or pancreatic resection, diarrhea, laxative abuse, GI inflammatory processes and chronic renal disease.^1,2

KMI Diagnostics Radioimmunoassay (RIA)

0.0−418.0 pg/mL

Pancreatic Polypeptide (PP) is a 36 amino acid linear oligopeptide, primary secreted by pancreatic islets of Langerhans cells.^3-6 Its specific role is not well clarified,⁷ but it is thought to regulate pancreatic and gastrointestinal secretions⁸ and hepatic glycogen levels.⁹ PP is generally considered a neuroendocrine differentiation marker with good specificity but low and variable sensitivity.^1,2,10 PP can be over-secreted by foregut neuroectodermal tumors as well as other tumors.^11,12 Measurement of PP has been recommended for the diagnosis of pancreatic neuroendocrine tumors (pNETs)¹³ and non-functioning pNETs.¹⁴ A 2012 Endocrine Society clinical practice guideline for multiple endocrine neoplasia type 1 (MEN1) recommended annual screening for emergence of pNETs by measuring levels of several serum tests in a gastrointestinal profile consisting of PP along with chromogranin A (CGA), and vasoactive intestinal polypeptide.¹⁵ However, two subsequent retrospectives found that, singly or in combination, these tests were not effective in early diagnosis of tumors.^16-18 The poor performance of these markers in screening for MEN1 was thought to likely be due to the low amounts of these peptides secreted by small tumors.¹⁸

While PP has been found to be elevated in the majority of patients with metastatic disease,¹⁹ less than half of patients with pNET present with elevated serum PP.²⁰ Detection of high levels of circulating PP, together with CGA is suggestive for pNETs.^3,10 Production of PP and/or CGA is observed in 100% of spontaneous and hereditary gastrinomas.²¹ A decline of PP level during patient monitoring is considered a good prognostic marker.²⁰