Generality
Calprotectin is a protein that binds substances such as calcium and zinc. It is found almost everywhere in the body, but is present above all in neutrophil granulocytes, monocytes and macrophages. During the performance of their defensive functions, these cells are able to trigger the inflammatory response against dangerous foreign agents.
The normal function of calprotectin is, therefore, to counteract the development of bacteria and fungi within the body ( antimicrobial activity ).
For this reason, calprotectin can be used as an indicator of inflammation in cases of chronic intestinal diseases, some infections of bacterial origin or tumors of the digestive system .
The fecal calprotectin dosage is the only test that can provide indications on the site of inflammation. The determination of the parameter in the plasma shows, instead, a phlogistic state that can be located everywhere. Moreover, in patients suffering from inflammatory bowel diseases (such as ulcerative colitis and Crohn's disease), the dosage of fecal calprotectin is a valid indicator of the degree of phlogosis
What's this
Calprotectin is a 36 kDa protein, capable of binding calcium and zinc; present a little in all the districts of the human body, it concentrates mainly in the cytoplasm of neutrophil granulocytes .
In lower concentrations, calprotectin is also present in monocytes and macrophages derived from them; these cells, similar to neutrophils, are white blood cells designed to gobble up - then to absorb, digest and destroy - foreign particles penetrated into the body, including microorganisms (to which neutrophils are most active).
Both neutrophils and macrophages have the ability to secrete chemical mediators of the inflammatory response.
Within these immune cells, calprotectin exhibits a high bacteriostatic and mycostatic activity; as such, it effectively counteracts the growth of fungi and bacteria.
Why do you measure
Since inflammatory processes are typically accompanied by an accumulation of neutrophil leukocytes and macrophages in inflamed tissues, calprotectin can be used as an indirect marker of inflammation . In fact, as explained above, the levels of calprotectin in the plasma tend to increase aspecifically in correspondence with inflammatory phenomena. Similarly, in intestinal inflammatory diseases, the concentration of calprotectin in the faeces rises sharply from the norm.
Calprotectin and inflammatory bowel disease
Calprotectin concentrations in faeces increase in correspondence to inflammatory diseases of the digestive tract, thus helping to distinguish chronic inflammatory diseases of the intestine (Crohn's disease, ulcerative colitis) from those on a dysfunctional basis (irritable bowel syndrome).
Several studies have shown that high levels of calprotectin in faeces have a better predictive significance, for inflammatory bowel diseases, than other typical inflammation markers, such as PCR and ESR.
The dosage of fecal calprotectin is in fact able to highlight inflammatory states in stages so mild or early as not to be sufficient to modify the values of VES or PCR. Furthermore, in faeces calprotectin is stable for up to seven days at room temperature, and for months if the material is frozen at -20 ° C.
Another important aspect, which contributes to raising the diagnostic usefulness of this test, is the independence of fecal values from phlogosis present in other parts of the body, which on the contrary can cause an increase in the aforementioned systemic inflammation markers.
In the search for intestinal inflammatory processes, faecal calprotectin proved to be more reliable also with respect to leukocyte counts or lactoferrin dosage.
When the examination is prescribed
Your doctor may request a fecal calprotectin test to understand what causes symptoms such as:
- Blood in the stool and / or diarrhea;
- Persistent abdominal pains and cramps (lasting more than a few days);
- Temperature;
- Weakness;
- Weight loss.
To confirm the suspicion of disease or to exclude from the diagnosis the conditions that cause similar signs, the dosage of calprotectin is often requested with other stool analyzes such as:
- coproculture;
- Examination of white blood cells in faeces;
- Occult blood research (FOBT).
The doctor may also prescribe blood tests to indicate the presence and severity of inflammation, such as erythrocyte sedimentation rate (ESR) and C-reactive protein (PCR).
Finally, for diagnostic confirmation of IBD, the patient can undergo an endoscopic examination (colonoscopy or sigmoidoscopy). This assessment allows to examine the intestine directly through the acquisition of images, and to take small pieces of tissue (biopsy) to verify the presence of inflammatory processes and determine whether histological changes have occurred.
Inflammatory bowel disease (IBD)
Inflammatory bowel diseases (IBD) are a group of chronic diseases characterized by inflammation and damage to the lining of the intestinal tract.
The causes of IBD are not yet fully known, but it is believed that some of these pathologies are due to an autoimmune process triggered by genetic predisposition, viruses and / or environmental factors.
The most common IBDs are Crohn's disease and ulcerative colitis. People suffering from these pathologies typically have acute moments alternating with periods of remission, during which the symptoms subside. The examination of fecal calprotectin is not specific for the diagnosis of IBD, but is carried out to determine and evaluate the stage of inflammation and is useful in monitoring the disease.
The evaluation of calprotectin allows:
- Determine if an inflammatory state of the intestine is in progress;
- Distinguish an inflammatory bowel disease (IBD) from other pathologies of the same tract that cause similar symptoms;
- Monitor the progression of an already diagnosed intestinal inflammatory disease.
Normal values
The reference values are slightly variable from laboratory to laboratory; as for the adult, they are indicatively included in the following limits:
- Negative <50 mg / Kg
- Weakly positive> 50 - 100 mg / Kg
- Positive> 100 mg / Kg
NOTE: in pediatric age the cut-off value of 50 mg / kg of faeces is valid from 4 years. In younger children, as well as in the elderly, normal values are much higher.
High Calprotectin - Causes
Substantial increases in calprotectin in the faeces are found mainly in chronic inflammatory bowel diseases (ulcerative colitis, Crohn's disease) and in neoplasms of the high-grade gastrointestinal tract.
As anticipated, faecal calprotectin is not increased in people with non-organic, often functional diseases, such as irritable bowel syndrome (IBS). On the other hand, it may increase in inflammatory, acute or chronic diseases, however limited to the digestive tract, such as peptic diseases, esophagitis, diverticulitis and infectious enterocolitis.
The elimination of calprotectin in the faeces is also a good marker of relapse in subjects suffering from inflammatory bowel disease, given its greatest increase in the clinically active phases of the disease.
High fecal calprotectin: the most common causes
- Ulcerative rectocolitis;
- Crohn's disease;
- Intestinal bacterial infections;
- Parassitossi;
- Colon cancer.
What to do if Calprotectin is high
High values of faecal calprotectin can lead the doctor to prescribe further diagnostic investigations, including invasive tests, such as colonoscopy and ileoscopy with histological examination or ultrasound of the abdomen.
The fact that faecal calprotectin concentrations are increased in neoplasms of the gastro-intestinal tract, in particular in colon-rectal cancer, justifies the greater reliability of fecal calprotectin as a screening test, compared to the detection of occult blood in faeces.
Low Calprotectin - Causes
If the test shows low levels of fecal calprotectin, there is a high possibility that there are no organic intestinal pathologies; consequently, the gastro-intestinal disorders that led the doctor to prescribe the examination are probably due to irritable bowel syndrome, other functional diseases or celiac disease.
How to measure it
The dosage of fecal calprotectin is performed on a small quantity of feces, collected in a special clean container. The sample should not be contaminated with water or urine.
Preparation
- Fasting is not required.
- Refrain from heavy physical activities in the two days preceding the test.
- Avoid having the calprotectin dosed in the faeces during the menstrual period or in the presence of intestinal bleeding (for example in the presence of hemorrhoids).
- In view of the examination, the doctor may suggest discontinuation of therapy with non-steroidal anti-inflammatory drugs (including aspirin) and gastric acid inhibitors. Do not stop taking these medicines on your own initiative and follow the medical guidelines accordingly.
In order to take into account daily changes in calprotectin levels, the doctor may request analysis of faecal samples taken on two consecutive days.
Interpretation of Results
The high concentration of fecal calprotectin indicates that an inflammation of the gastrointestinal tract has been established: the higher the concentration, the more inflammation is severe.
High fecal calprotectin
The increase in calprotectin in faeces has been observed in the case of:
- Inflammatory bowel diseases (ulcerative colitis, Crohn's disease);
- Various inflammations of the digestive system (peptic ulcer, esophagitis, diverticulitis);
- Bacterial and parasitic infections;
- Tumor forms.
There is no increase, however, in non-inflammatory, but functional disorders.
However, to determine the exact cause of the inflammation and the symptoms that the patient reports, further investigations, such as colonoscopy or ultrasound of the abdomen, are often necessary.
Low fecal calprotectin
Low calprotectin values have no particular significance, other than to exclude the presence of inflammatory bowel diseases.
A reduced concentration of calprotectin may signal the presence of a viral infection or colon-irritable syndrome; in these cases, endoscopy is less indicated.
