Calprotectin Test

What is Calprotectin?

Calprotectin is a protein that can be found in your faeces (also called stools or poo) when your intestine (gut) becomes inflamed. Calprotectin plays a major role in inflammation. It originates in the white blood cells, which travel into the inflamed gut tissue during the inflammatory process.

What is a Calprotectin Test?

The calprotectin in faeces is used as a biomarker for inflammation in the gut. It is very sensitive biomarker for gut inflammation because faeces are in contact with the wall of the gut. In a laboratory, calprotectin is extracted from the faeces sample. The calprotectin is then detected using a method known as an ELISA (enzyme-linked immunosorbent assay). The calprotectin concentration detected in the sample has been shown to correlate well with the amount of inflammation in your gut.

Why is a Calprotectin Test important?

A faecal calprotectin test is used when gut inflammation is suspected. Inflammation of the gut is characteristic of the condition known as inflammatory bowel disease (IBD), which includes ulcerative colitis and Crohn's disease. Faecal calprotectin may also be a biomarker of colorectal cancer and some polyp types.

Faecal calprotectin can be used in the diagnosis and monitoring of disease activity and gut tissue healing. It can also help to guide treatment, since it can be used to determine the efficacy of a medicine in promoting gut tissue healing, and to predict return of the disease when treatment is stopped. The symptoms of IBD and irritable bowel syndrome (IBS) can be very similar, and faecal calprotectin is very helpful in differentiating between the two conditions. Importantly, the test prevents people with IBS from undergoing unnecessary diagnostic procedures, which are usually required for people with suspected IBD.

Who should have a Calprotectin test?

A faecal calprotectin test may be requested if you have symptoms of gut inflammation, other symptoms suggesting IBD, or have had a change in your bowel movements for at least six weeks. Symptoms include diarrhoea, abdominal pain and cramps, bloating, rectal bleeding, blood in your faeces, tiredness, and body weight loss.

How to take a stool sample for Calprotectin testing?

A sample of your faeces can be self-collected during the day or night. You are provided with instructions on how to collect the sample, as well as a sample collection pack containing all items required for sample collection.

Briefly, you should complete the labels and label the brown-lid collection tube before collecting the sample. To collect your faeces, put toilet paper in the toilet bowl, then poo onto the toilet paper. Try to avoid letting the faeces get wet with water in the toilet. Wash your hands after pooing. The sampling stick attached to the collection tube lid is then scraped over the faeces, evenly covering the stick. Then the sampling stick is returned to the collection tube and the tube is closed. Wash your hands again. Then put the collection tube into the outer sample container (this contains absorbent material) and close. Now place the sample container plus the request form into the test-kit box, and place the test kit box into the blue envelope for posting. Post the sample immediately for analysis. Results take 5 days from when the sample is booked in at the laboratory.

What do Calprotectin Test results indicate?

The calprotectin test result will determine if you do or do not have active inflammation of the gut. The thresholds for a positive and negative result differs from test to test, depending on the manufacturer of the calprotectin test. The higher the calprotectin level, the more inflammation in your gut.

A positive test result means that your faecal calprotectin level is above 100 µg/g, and is considered to be high. In this case, you will likely be referred by your doctor to a hospital gastroenterology clinic for further investigations (such as colonoscopy) to find out the cause of the high calprotectin level.

A negative test result means that your faecal calprotectin level is below 50 µg/g, and is normal. This suggests that your symptoms are unlikely be due to IBD. However, it does not necessarily mean that you do not have a problem with your gut. If you continue to have symptoms your doctor will probably investigate for other gut conditions, such as IBS, gluten intolerance (coeliac disease), and food allergies.

If your test result falls within the range 50–100 µg/g, then its interpretation is less certain – your calprotectin level is above the threshold for a negative result but below that of a positive result.

Fluctuations in calprotectin levels to above normal can occur due to inflammatory conditions other than IBD, including bacterial infections, mild diverticulitis (inflammation of the gut diverticula – small pouches in the gut lining), irritants of the gut lining, and certain medications (e.g., proton pump inhibitors that reduce stomach acid). In such cases, your doctor may want to repeat the test in 2 to 3 weeks to reassess your calprotectin level.

What do normal Calprotectin Test results indicate in people with IBD?

If you have previously been diagnosed with IBD, and you have a negative calprotectin test result, then it most likely means that your IBD is in remission and that your treatment is working. It does not mean that you are cured, since IBD is a life-long disease for which there is no cure.

You should be aware that faecal calprotectin tests measure inflammation in the lower sections of your gut (the small and large intestine), so normal calprotectin levels do not rule out inflammation in the upper sections of your intestine.

Reviewed by: Dr Loraine Haslam MBBS, DRCOG, DFSRH, LoC SDI, LoC IUT, MRCGP
GMC registration number: 4524038
Date: 24 November 2022
Next review: 23 November 2024
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