Faecal Calprotectin Test: What a High Result Means

Why this matters

Faecal means relating to stool (poo), so a faecal calprotectin test is done on a small stool sample. Ongoing diarrhoea, tummy pain and bloating can come from very different causes. Irritable bowel syndrome (IBS) is common and does not damage the gut. Inflammatory bowel disease (IBD), which includes Crohn's disease and ulcerative colitis, involves inflammation that needs treatment. Inflammation is the body's response to injury or irritation, and in the bowel it can cause pain, diarrhoea and damage to the lining. Faecal calprotectin is one of the tests used to help tell the two apart.

What calprotectin is

Calprotectin is a protein found mainly in neutrophils, a type of white blood cell that the immune system sends to areas of inflammation. When the lining of the bowel is inflamed, neutrophils move into it and calprotectin passes into the stool. The more inflammation, the higher the level tends to be.

How results are usually read

Results are reported in micrograms per gram (µg/g), meaning how much calprotectin is found in each gram of stool. Many laboratories use 50 micrograms per gram as the cut-off for a normal result, though ranges vary between labs. A normal result in an adult with gut symptoms makes IBD less likely. Results just above the cut-off are often repeated after a few weeks, because levels can rise for a short time. Higher results are more likely to reflect ongoing inflammation and usually lead to referral for further investigation.

What else can raise it

Calprotectin shows that inflammation is present, not what is causing it. Levels can also be raised by gut infections, some medicines including anti-inflammatory painkillers such as ibuprofen, coeliac disease, diverticular disease (small pouches in the bowel wall that can become inflamed) and, less commonly, polyps (small growths on the bowel lining) or bowel cancer. That is why a high result is followed up rather than treated as a diagnosis.

How it relates to other gut markers

Calprotectin is often measured alongside other stool markers. Secretory IgA is an antibody, a protein made by the immune system, produced in the gut lining as part of its first line of defence; it gives an indication of how those defences are working. A faecal immunochemical test (FIT) looks for small amounts of blood in stool that cannot be seen. A positive FIT result should always be discussed with your GP promptly, whatever your calprotectin level.

What you could do

A calprotectin result is most useful alongside a clear picture of your symptoms.

• Note how often you open your bowels, the consistency, and whether there is blood or mucus
• Tell your clinician about any anti-inflammatory painkillers you take, as they can affect the result
• If your result is raised, ask whether a repeat test or referral is the next step, and keep tracking symptoms in the meantime

This article is for general information only and is not a substitute for medical advice. If you are worried about your health or your results, speak to your GP or specialist team. In an emergency, call 999 or go to A&E.

References:

NICE, 'Faecal calprotectin diagnostic tests for inflammatory diseases of the bowel' (DG11) https://www.nice.org.uk/guidance/dg11

NHS, 'Inflammatory bowel disease' https://www.nhs.uk/conditions/inflammatory-bowel-disease/