Gastrin Test

Your doctors may order this test if you have acidity, recurring peptic ulcer or other symptoms that are suggestive of gastrinoma. These symptoms include:

• Abdominal pain – a burning type of pain in the stomach which is worsened by hunger and relieved temporarily by eating. The pain continues off and on for a long period.
• Diarrhoea
• Nausea and vomiting
• Loss of appetite
• Weight loss

The test may also be performed to check for other conditions that cause high gastrin levels such as G-cell hyperplasia and pernicious anaemia. G-cell hyperplasia is a condition caused due to an increased number of G cells in the stomach and is characterised by markedly high gastrin secretion. 

In pernicious anaemia, the cells that secrete acid in the stomach are destroyed. The reduced acidity results in increased activity of the G cells and high gastrin production. 

Additionally, gastrin test is helpful in diagnosing Zollinger-Ellison syndrome, which is associated with very high gastrin levels. If your gastrin levels are moderately high and the doctor suspects this condition, he/she may order a gastrin stimulation test. In this test, your doctor will check your gastrin levels, then give you an injection - usually of the hormone secretin to stimulate gastrin secretion - and then check the gastrin levels again. If you have Zollinger-Ellison syndrome, your gastrin levels will increase markedly after the injection.

Gastrin test may also be ordered periodically after surgical removal of a gastrinoma to check for tumour recurrence.

Fasting for 12 hours is required before this test. Water is allowed; however, do not drink tea or coffee before the test. Also, avoid alcohol for 24 hours before the test. Do not go for any imaging studies that use radioactive materials at least one week before the test.

Inform your doctor if you are taking any medicines and supplements. Certain medicines may affect the results of this test. Medicines that increase gastrin levels include acid-suppressive medications (such as antacids, ranitidine and omeprazole), calcium supplements, beta-blockers and insulin. Medicines that decrease gastrin levels include calcium salts, tricyclic antidepressants, steroids, anticholinergics, caffeine and adrenergic blockers. Protein-rich foods and peptic ulcer surgery can also affect the results of the gastrin test.

You may be asked to discontinue proton pump inhibitors (such as omeprazole) one week before the test and H2-receptor blockers (such as cimetidine) at least three days before the test. Do not stop taking any regular medicine on your own.

It is a simple blood test. A nurse or laboratory technician will collect a blood sample from a vein in your arm using a sterile needle. The sample will be transported to the laboratory in a container filled with ice within one hour of collection. Results are usually obtained within a day or two.

After the test, you may feel slight soreness at the needle insertion site, however, it will subside soon. Few side effects of drawing a blood sample include:

• Haematoma (accumulation of blood under the skin) at the site of needle insertion
• Infection 
• Excessive bleeding at the site of needle insertion

Normal results: 

Normal values of gastrin levels in the blood are as follows:

• Fasting: < 25-100 pg/mL (picograms per millilitre) in adults and 10-125 pg/mL in children
• After meals: 95-140 pg/mL

This reference range may vary slightly from one laboratory to another. Please consult your doctor for an accurate interpretation of your results.

Abnormal results: 

Higher or lower than normal gastrin levels are considered abnormal. 

High levels of gastrin are seen in conditions such as:

• Stomach cancer
• Zollinger-Ellison syndrome (gastrin levels > 500 pg/mL)
• Stomach and duodenal ulcers
• Pernicious anaemia
• End-stage kidney disease
• G-cell hyperplasia 
• Hyperparathyroidism
• Pyloric obstruction (blockage in the outlet of the stomach)

Low levels of gastrin are found in conditions such as:

• Hypothyroidism (decreased secretion of thyroid hormone)
• After a stomach surgery called antrectomy with vagotomy

Disclaimer: All results must be clinically correlated with the patient’s complaints to make a complete and accurate diagnosis. The above information is provided from a purely educational point of view and is in no way a substitute for medical advice by a qualified doctor.