Type of test Blood

Normal findings

 Adult: 0-180 pg/mL or 0-180 ng/L (SI units) Levels are higher in elderly patients.

Child: 0-125 pg/mL

Test explanation and related physiology

 Zollinger-Ellison (ZE) syndrome (gastrin-producing pancreatic tumor) and G-cell hyperplasia (overfunctioning of G cells in the distal stomach) are associated with high serum gastrin levels. Patients with these tumors have aggressive peptic ulcer disease. Unlike a patient with routine peptic ulcers, a patient with ZE syndrome or G-cell hyperplasia has a high incidence of complicated and recurrent peptic ulcers. It is important to identify this latter group of patients to institute more appropriate, aggressive medical and surgical therapy. The serum gastrin level is normal in patients with routine peptic ulcer and greatly elevated in patients with ZE syndrome or G-cell hyperplasia.

It is important to note that patients who are taking antacid peptic ulcer medicines or have had peptic ulcer surgery or have atrophic gastritis will have a high serum gastrin level. However, levels usually are not as high as in patients with ZE syndrome or G-cell hyperplasia.

Not all patients with ZE syndrome exhibit increased levels of serum gastrin. Some may have top normal gastrin levels, which makes these patients difficult to differentiate from patients with routine peptic ulcer disease. ZE syndrome or G-cell hyperplasia can be diagnosed in these top normal patients by gastrin stimula tion tests with the use of calcium or secretin. Patients with these diseases have greatly increased serum gastrin levels associated with the infusion of these drugs.

 Interfering factors

• Peptic ulcer surgery creates a persistent alkaline environment, which is the strongest stimulant to gastrin.

 • Ingestion of high-protein food can result in an increase in serum gastrin two to five times the normal level.

* Patients with diabetes who take insulin may have falsely increased levels.

* Drugs that may increase serum gastrin levels include antacids and H₂-blocking agents (e.g., esomeprazole, lansoprazole, omeprazole, pantoprazole, rabeprazole).

* Drugs that may decrease levels include anticholinergics and tricyclic antidepressants.

Procedure and patient care

 • See inside front cover for Routine Blood Testing.

 • Fasting: yes

• Blood tube commonly used:

* red Tell the patient to avoid alcohol for at least 24 hours.

• For the calcium infusion test, administer calcium gluconate intravenously. A preinfusion serum gastrin level is then compared with specimens taken every 30 minutes for 4 hours.

 • For the secretin test, administer secretin (0.4 ug/kg) intrave nously over 1 minute. Preinjection and postinjection serum gastrin levels are taken at 2, 5, 10, 15, and 20 minutes after injection.

Abnormal findings

 Increased levels

- Zollinger-Ellison syndrome

- G-cell hyperplasia

- Pernicious anemia

- Atrophic gastritis

- Gastric carcinoma

- Chronic renal failure

- Pyloric obstruction or gastric outlet obstruction

- Retained antrum after gastric surgery