Pancreatic polypeptide (PP) normal values increase with age (approximately 20 pg/mL per decade).
Nonfasting state results in falsely elevated values.
The sham feeding test is invalid if food is swallowed. Ingestion of food typically results in a significant and prolonged PP increase over baseline (typically >200 pg/mL).
This test should not be requested in patients who have recently received radioisotopes, therapeutically or diagnostically, because of potential assay interference. A recommended time period before collection cannot be made because it will depend on the isotope administered, the dose given, and the clearance rate in the individual patient. Specimens will be screened for radioactivity prior to analysis. Radioactive specimens received in the laboratory will be held and assayed after the radioactivity has sufficiently decayed. This will result in a test delay.