In the blood, red cells perform the vital role of delivering oxygen and removing carbon dioxide from around the body by virtue of the haemoglobin they contain. The role of white cells is to help defend the body against infection and foreign substances. Calprotectin is a protein that is found in white blood cells and it has strong antibacterial and antifungal properties. There is as much calprotectin in the white cells that carry it, as there is haemoglobin in red cells.
Calprotectin is activated when inflammation occurs (whatever the cause of that may be) and thus can be used as a diagnostic indicator. The concentration of calprotectin relates directly to the severity of the inflammation. Figure 1. represents the calprotectin concentrations measured in faecal samples from patients diagnosed with Crohn’s Disease and shows increasing levels with progression of the condition.
Thus, when lower abdominal symptoms exist, a faecal calprotectin test is used to identify whether an inflammatory bowel condition that requires further investigation, is the possible cause.
Faecal calprotectin has proven to be an extremely useful and cost effective marker to help differentiate between IBD (Inflammatory Bowel Disease) and IBS (Irritable Bowel Syndrome) and gained approval from NICE at the end of 2013 for screening purposes. Since then the volume of calprotectin testing has increased dramatically. It has no doubt saved many patients from unnecessary colonoscopies and helped in the diagnosis of those with some form of inflammatory bowel disease (IBD) e.g. Crohn’s Disease (CD) or Ulcerative Colitis (UC).
It is widely accepted that a calprotectin result of <50 µg/g is negative – this doesn’t mean that there is nothing wrong, just that the symptoms are unlikely to be caused by IBD. If symptoms persist but the calprotectin level is negative then other causes for the symptoms need to be investigated e.g. Irritable Bowel Syndrome (IBS), coeliac disease, food allergies or intolerances.
Faecal calprotectin levels >200 µg/g are usually considered positive and in most cases will result in a referral to the gastroenterology unit at the local hospital, so that further investigations can be performed to determine the cause of these increased values.
Results in the middle range or grey zone (50 – 200 µg/g) provide less certainty. The level is elevated above normal but is still lower than a positive result. There are a number of things that can cause the calprotectin level to moderately or even transiently increase without the cause being IBD:
When values are in this region with no obvious explanation (such as medication) the recommendation is to repeat the test in 2 – 3 weeks to see if the level has dropped back to more normal levels or has continued to rise and hence needs to be investigated further.
Calprotectin is purely a marker of inflammation; the problem is that any number of things can have caused this. Although faecal calprotectin has proved an invaluable tool for diagnosing and monitoring IBD, it is the whole clinical picture that determines the diagnosis and this is what healthcare professionals use to make a judgement. If symptoms persist, whether the calprotectin levels are high or low then you should seek further advice from your healthcare professional.
Living with Crohn’s Disease – Lee Stanley discusses why regular self testing of his faecal calprotectin levels would be beneficial
Calprotectin enters the stool whilst it is contact with the gut wall, and the concentration will vary depending on the transit time of the gut contents. If things are moving rapidly then it may not collect much calprotectin! For this reason it is recommended that the first stool of the day is used – this is likely to have been in the gut overnight and so should contain the highest level of calprotectin. If the first stool isn’t possible then use a sample where there has been a reasonable time between bowel movements.
Empty the bladder before collecting the sample to avoid contamination and dilution with urine.
The sample must not come into contact with the toilet water which may contain chemicals that could influence the test result.
Calprotectin is not evenly distributed in the stool sample, so a sensible amount needs to be sent to the laboratory for testing – too little and there may be no calprotectin in the portion sent. Half fill the sample container with stool and seal tightly – ensure your full name and the date is on the pot. Please don’t completely fill the container in case of leaks!
Return the sample to the surgery/hospital within 24 hours.
PLEASE NOTE: The information on this site is primarily designed for use by healthcare professionals rather than the general public. Similarly the products are not suitable for personal purchase and self-testing without direction from a doctor. If you have any concerns about Calprotectin testing or IBD, IBS and related conditions, please speak to your GP.