Gastrin


Sunquest Code:GASTRN  
Epic Code:LAB80Epic Name:GASTRIN
Methodology:Chemiluminescent immunoassay
CPT Code:82941
Turnaround Time:Specimens are sent to reference laboratory Mon-Sat; results are reported in 1-2 days.


Collection Instructions

Specimen:Blood
Optimal Volume:2 mL
Minimum\Peds Volume:1.2 mL
Container:Red or gold (gel) (Red (no gel))
Patient Preparation:12 hour fast recommended.
Causes for Rejection:Plasma and nonfrozen specimens, grossly hemolyzed or lipemic specimens.


Processing and Shipping

Specimen Processing:Centrifuge and aliquot 1 mL, 0.5 mL minimum. Samples are stable refrigerated for 7 days.
Shipping Instructions:Ship on dry ice.
Test Performed at or Referral Lab Lab Sendouts  (ARUP)
Referral Lab number:70075 (GAST)


Interpretive

Reference Range:0-100 pg/mL
Use:

Gastrin, a major gastrointestinal hormone, serves to stimulate gastric acid secretion. Gastrin testing is helpful in the identification of Zollinger-Ellison tumors (gastrinomas) and other causes of hypergastrinemia. In fasting subjects, gastrin normally circulates at levels less than 100 pg/mL. A gastrin pH less than 5.0 and a serum gastrin greater than 1000 pg/mL are virtually diagnostic of ZES. Fasting gastrin levels greater than 500 pg/mL are consistent with patients with Zollinger-Ellison syndrome (ZES), but 40% of patients with ZES have values between 100-500 pg/mL and require a stimulation test for further assessment. Most patients with Zollinger-Ellison syndrome have serum gastrin concentrations between 150-1000 pg/mL (71-475 pmol/L). Hypergastrinemia may also present in patients with normal or slightly increased gastric acid secretion, including patients with achlorhydria (atrophric gastritis or pernicious anemia), renal insufficiency, massive small bowel resection, G-cell hyperplasia, gastric outlet obstruction, and retained gastric antrum, as well as in patients receiving potent antisecretory drugs. The differentiation between Zollinger-Ellison syndrome and patients with hypergastrinemia without gastrinoma can be aided by “provocative” tests (e.g. secretion challenge or calcium infusion test). In the secretion challenge test, greater than 95% of gastrinoma patients respond to secretin infusion with a significant elevation of gastrin levels above basal levels (a rise of at least 200 pg/mL).

 

Secretin Stimulation Test for Diagnosis of Gastrinoma (Zollinger-Ellison Syndrome)

Patient Preparation: Subject should be fasting on the day of study. Acid suppressive medications should be discontinued well in advance to avoid effects on gastrin release. Baseline blood samples are taken 5 minutes and immediately prior to (time-5 min and 0 min) secretin administration. Pure porcine secretin (2 units/kg) is given IV over a 30 second period. Serum samples are taken at 2 and 5 minutes after injection, and then at 5 minute intervals for 20 minutes.

Contraindications: Secretin testing should not be performed in patients with acute pancreatitis.

Interpretation of Results: Baseline serum gastrin in patients with gastrinoma is greater than 150 pg/mL. A positive secretin stimulation test demonstrates a quick and substantial increase in serum gastrin (by more than 200 pg/mL) and occurs in over 85 percent of patients with proven gastrinoma.

Comments: Achlorhydria or profound hypochlorhydria can result in increased fasting serum gastrin levels and an exaggerated response to IV secretin stimulation. Proton pump-inhibiting medications should be discontinued 5 days before the test and patients placed on a H-2 receptor antagonist, which should be discontinued 24 hours prior to testing.

 

 



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