Gastrin (Sendout)

Useful For:

• Investigation of patients with achlorhydria or pernicious anemia
• Investigation of patients suspected of having Zollinger-Ellison syndrome
• Diagnosis of gastrinoma

Patient Preparation:

• Fasting (8 hours) required
• For 12 hours before specimen collection, the patient refrain from taking multivitamins or dietary supplements (eg, hair, skin, and nail supplements) containing biotin (vitamin B7).
• For 1 week before specimen collection, if medically feasible, patient refrain from taking proton pump inhibitors (omeprazole, lansoprazole, dexlansoprazole, esomeprazole, pantoprazole, and rabeprazole).
• For at least 2 weeks before specimen collection, patient should refrain from taking or receiving drugs that interfere with gastrointestinal motility (eg, opioids).

Reference Range: <100 pg/mL

There is no evidence that fasting serum gastrin levels differ between adults and children. Although 8-hour fasts are difficult or impossible to enforce in small children, serum gastrin levels after shorter fasting periods (3-8 hours) may be 50% to 60% higher than the 8-hour fasting value.

See also Mayo International System of Units (SI) conversion for Reference Values.

Cautions:

Isolated serum gastrin levels can only be interpreted in fasting patients; nonfasting specimens are uninterpretable.

Artifactual hypergastrinemia may be observed in fasting patients who have undergone procedures that result in temporary gastric distention or dysmotility (eg, after gastroscopy).

Kidney failure prolongs the serum half-life of gastrin and is associated with increased serum gastrin levels.

In rare cases, some individuals can develop antibodies to mouse or other animal antibodies (often referred to as human anti-mouse antibodies [HAMA] or heterophile antibodies), which may cause interference in some immunoassays. Caution should be used in interpretation of results, and the laboratory should be alerted if the result does not correlate with the clinical presentation.

Drugs that interfere with gastric acid secretion, in particular proton pump inhibitors (eg, omeprazole, pantoprazole, dexlansoprazole, lansoprazole, rabeprazole), can lead to significant elevations of serum gastrin levels often above the normal range. These drugs can be discontinued, if feasible, for at least 1 week before serum gastrin measurement in order to avoid gastrin elevation.

Drugs that interfere with gastrointestinal motility (eg, opioids) may also interfere with serum gastrin testing.

Outside Laboratories: Centrifuge sample and aliquot serum into a separate plastic vial within 2 hours of collection. Freeze serum at -20°C.

Stability: Frozen (preferred): 30 days; Refrigerated: 24 hours; Ambient: Unacceptable.

Reject Due To: Gross hemolysis.

Centrifuge sample and aliquot serum into a separate plastic vial within 2 hours of collection. Freeze serum at -20°C.

• Note: For serial collections, the collection interval (Baseline, 15 min, 30 min, 60 min, etc.) should be added to the modifier if provided.

Sendouts:

• Order Mayo Test: GAST
• Interfaced: Yes [Interface: 601; Worksheet: MAFZ]
• For serial collections, add the collection interval information (e.g. Baseline, 15 min, 30 min, etc.) for each order to the Report Notes field in MayoAccess prior to closing the batch.

Stability: Frozen (preferred): 30 days; Refrigerated: 24 hours; Ambient: Unacceptable.

Reject Due To: Gross hemolysis.