Specimen Collection:
Gastrin levels can only be interpreted in fasting (>10 hours) patients; non-fasting specimens are uninterpretable.
Sample needs to be sent to the lab to be separated and frozen immediately. Place the yellow Urgent Gastrin Label on the request form at the time of blood collection.
Oxalate, heparin and EDTA are unacceptable sample types.
Grossly Lipemic and haemolysed samples should be avoided.
Diagnostic Use and Interpretation:
Increased in Zollinger-Ellison syndrome (ZES) from gastrinoma. In 25% of the cases, gastrinoma is part of the Multiple Endocrine Neoplasma type 1 (MEN type 1) syndrome.
A fasting serum gastrin concentration > 477 pmol/L (1000 ng/L), together with a gastric acid pH <=2 is virtually diagnostic of gastrinoma. However, note that 68% of gastrinoma patients have a fasting gastrin concentration between 47.7 to 477pmol/L (100 to 1000 ng/L) and 0.3-3% even exhibit normal fasting gastrin level. and a stimulation test (secretin or calcium infusion) is required to confirm the diagnosis. These stimulation tests are conducted under fixed protocol and close supervision at Greenlane Endocrinology department.
Other than gastrinoma (sporadic ZES or associated with MEN-1), antral predominant Helicobacter pylori gastritis, pyloric obstruction, post gastric resection with intact antrum (e.g. Billroth type II), renal failure are other causes of increased fasting gastrin concentration with acidic gastric pH 2 include: chronic atrophic gastritis associated with pernicious anaemia or with chronic Helicobacter pylori infection; postvagotomy; use of proton pump inhibitor and H2 receptor antagonist therapy. There 2 classes of acid reduction therapy generally will not cause gastrin level to rise above 400 pmol/L (832 ng/L). Patients must be off these drugs for at least 1 week for valid interpretation of an elevated gastrin. If there is strong suspicion of underlying ZES and worry of precipitating peptic ulcer disease, the proton pump inhibitors may be substitued by a H2 receptor antagonist. Fasting gastrin level is to be measured after withholding oral H2 receptor blocker for 30 hours and withholding intravenous H2 receptor antagonist infusion for 12 hours.
Infection by Helicobacter pylori usually results in about 2 fold rise in basal serum gastrin concentration and up to six fold increase following meal. The raised gastrin concentration generally returns to normal 6 months post eradication therapy.
References:
1. Dhillo et al. Plasma gastrin cannot be used to diagnose gastrinoma in patients on proton pump inhibitors or H2 - receptor antagonists. Ann Clin Biochem. 2006; 43:153.
2. Murgesan SVM et al. Review article: strategies to determine whether hypergastrinaemia is due to Zollinger - Ellison syndrome rather than a more common benign cause. Aliement Pharm Therap 2009; 29:1055-68
Laboratory Notes
Any queries please contact Section Leader/Technical Specialist SCP - Endocrinology
Patient preparation : Fast overnight for > 10 hours
Sample: Serum (Plain) only
Sample stability Must be separated within 1 hour
Sample preparation : Separate and freeze within 1 hour
Minimal volume: greater than 1 mL
Transport to Canterbury Health Labs Send frozen