La calprotectina it is a protein that binds substances such as calcium and zinc. It is found almost everywhere in the organism, but it is mainly present inside neutrophilic granulocytes, monocytes and macrophages. While carrying out their defensive functions, these cells are able to trigger the inflammatory response towards dangerous foreign agents.
The normal function of calprotectin is, therefore, to counteract the development of bacteria and fungi within the body (antimicrobial activity).
In the presence of inflammation in the gastrointestinal tract, white blood cells migrate to it and release the protein, the concentration of which in the stool increases accordingly.
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.
Calprotectin is a 36 kDa protein, capable of binding calcium and zinc; present in all parts of the human body, it is mainly concentrated in the cytoplasm of neutrophil granulocytes.
In lower concentrations, calprotectin is also present in moles monocytes And in the macrophages which derive from them; these cells, similar to neutrophils, are white blood cells designed to phagocytize - therefore to englobe, digest and destroy - foreign particles that have entered the body, including microorganisms (towards which neutrophils are more active).
Both neutrophils and macrophages have the ability to secrete chemical mediators of the inflammatory response.
Within these immune cells, calprotectin exhibits high bacteriostatic and mycostatic activity; as such, it effectively counteracts the growth of fungi and bacteria.
Because it is measured
Since inflammatory processes are typically accompanied by an accumulation of neutrophilic leukocytes and macrophages in inflamed tissues, calprotectin can be used as a indirect marker of inflammation. In fact, as explained above, the levels of calprotectin in the plasma tend to increase in a non-specific way in correspondence with inflammatory phenomena. Similarly, in intestinal inflammatory diseases, the concentration of calprotectin in the faeces rises significantly compared to the norm.
Calprotectin and inflammatory bowel diseases
The concentrations of calprotectin in the faeces increase in correspondence with 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 elevated levels of calprotectin in stool have a better predictive significance for inflammatory bowel disease than other typical markers of inflammation, such as CRP and ESR.
The dosage of fecal calprotectin is in fact able to highlight inflammatory states in such mild or early stages as not to be sufficient to modify the ESR or CRP values. In addition, calprotectin is stable in faeces 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 increasing the diagnostic usefulness of this examination, is the independence of the fecal values from the inflammation present in other parts of the body, which on the contrary can cause an increase in the aforementioned systemic markers of inflammation.
In the search for intestinal inflammatory processes, fecal calprotectin has also been shown to be more reliable than the leukocyte count or the lactoferrin dosage.
When the examination is prescribed
Doctors may request fecal calprotectin test to determine what is causing symptoms such as:
- Blood in the stool and / or diarrhea;
- Persistent abdominal pain and cramps (lasting more than a few days);
- Weight loss.
To confirm suspicion of disease or exclude conditions causing similar signs from the diagnosis, calprotectin testing is often asked with other stool tests such as:
- Testing of white blood cells in stool
- Occult blood research (FOBT).
Your doctor may also order blood tests to indicate the presence and severity of inflammation, such as erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP).
Finally, for diagnostic confirmation of IBD, the patient may undergo an endoscopic examination (colonoscopy or sigmoidoscopy). This assessment allows to directly examine the intestine through the acquisition of images, and to take small pieces of tissue (biopsy) to check for the presence of inflammatory processes and determine if histological changes have occurred.
Calprotectin evaluation allows you to:
- Determine if an inflammatory state of the intestine is in progress;
- Distinguish inflammatory bowel disease (IBD) from other pathologies of the same tract that cause similar symptoms;
- Monitor the progression of an already diagnosed inflammatory bowel disease.
The reference values are slightly variable from laboratory to laboratory; as regards the adult, they are indicatively included in the following limits:
- Negative <50 mg / Kg
- Weakly positive> 50 - 100 mg / Kg
- Positivo > 100 mg/Kg
NOTE: in pediatric age, the cut-off value of 50 mg / kg of feces is valid from 4 years of age. In younger children, as well as in the elderly, normal values are significantly higher.
Calprotectina Alta - Cause
Substantial elevations of calprotectin in faeces are found mainly in chronic inflammatory bowel diseases (ulcerative colitis, Crohn's disease) and in high-grade gastrointestinal tract neoplasms.
As anticipated, fecal calprotectin is not increased in people with inorganic diseases, often of a functional type, such as irritable bowel syndrome (IBS). On the other hand, it can increase in inflammatory, acute or chronic pathologies, 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 diseases, given its greater increase in the clinically active phases of the disease.
What to do if Calprotectin is elevated
Elevated fecal calprotectin values may prompt the physician to order further diagnostic tests, including invasive tests, such as colonoscopy and ileoscopy with histological examination or ultrasound of the abdomen.
The fact that fecal concentrations of calprotectin are increased in neoplasms of the gastrointestinal tract, particularly in colorectal cancer, justifies the greater reliability of fecal calprotectin as a screening test, compared to the evidence of occult blood in the faeces.
Calprotectina Bassa - Cause
If the test shows low levels of fecal calprotectin, there is a high possibility that there are no intestinal organic pathologies; consequently, the gastrointestinal disorders that led the doctor to prescribe the examination are probably attributable to irritable bowel syndrome, other functional pathologies or celiac disease.
How it is measured
The dosage of fecal calprotectin is performed on a small amount of feces, collected in a special clean container. The sample must not be contaminated with water or urine.
- Fasting is not required.
- Refrain from strenuous physical activity in the two days leading up to the test.
- Avoid undergoing the dosage of calprotectin in the stool during the menstrual period or in the presence of intestinal bleeding situations (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 comply with medical guidelines to do so.
In order to account for the daily changes in calprotectin levels, the doctor may request the analysis of fecal samples taken on two consecutive days.
Interpretation of Results
The high concentration of fecal calprotectin indicates that inflammation of the gastrointestinal tract has established: the higher the concentration, the more severe the inflammation.
High fecal calprotectin
The increase in calprotectin in faeces has been observed in cases of:
- Chronic 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, further tests, such as a colonoscopy or ultrasound of the abdomen, are often required to determine the exact cause of the inflammation and the symptoms the patient is reporting.
Low fecal calprotectin
Low calprotectin values have no particular significance, other than to exclude the presence of inflammatory bowel diseases.
A low concentration of calprotectin can signal the presence of a viral infection or irritable bowel syndrome; in these cases, endoscopy is less indicated.