Calprotectin is a calcium-binding protein produced by neutrophils and monocytes, and it may be involved in inflammatory signalling. Elevated Calprotectin and faecal Lactoferrin levels indicate the presence of neutrophils and inflammation in the gastrointestinal (GI) mucosa. Calprotectin and Lactoferrin differentiate between irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD). IBD includes autoimmune conditions such as Crohn’s disease and ulcerative colitis (UC); these conditions may become life-threatening and require lifelong treatment.
Multiple studies have shown faecal Calprotectin and Lactoferrin to be equivalent with respect to clinical sensitivity and specificity. Studies suggest that Calprotectin may correlate more closely with histological (cell microscopy) findings. Lactoferrin may correlate better to macroscopic (endoscopy) findings, and may be the better indicator of impending relapse, elevating 2-3 weeks prior to clinical symptoms.
Chronic inflammation of the gastrointestinal mucosa contributes to symptoms of IBD. Chronic stress is known to contribute to symptom flare-ups and increased inflammation. Liver disease or the use of aspirin or nonsteroidal anti-inflammatory (NSAID) medications may elevate Calprotectin levels. Faecal Calprotectin levels may also be increased in new-borns.
Faecal lactoferrin is a biomarker of serious gastrointestinal inflammation. Faecal lactoferrin is elevated in association with Inflammatory Bowel Disease (IBD) such as Ulcerative Colitis (UC) or Crohn's Disease (CD), but NOT Irritable Bowel Syndrome (IBS). Therefore, assessment of faecal lactoferrin levels enables distinction between IBD and non-inflammatory IBS
Moderate elevations in faecal lysozyme are commonly associated with significant overgrowth of enteropathogenesis such as yeast or dysbiotic bacteria. Markedly elevated levels of faecal lysozyme have been identified in colonic inflammatory bowel disease (IBD), such as Crohn's disease and ulcerative colitis as well as other non-IBD G.I. diseases with diarrhoea, compared to healthy controls.
Immunological activity in the gastrointestinal tract can be assessed using secretory immunoglobulin A (sIgA). Secretory IgA is the predominant antibody, or immune protein the body manufactures and releases in external secretions such as saliva, tears, and milk. It is also transported through the epithelial cells that line the intestines out into the lumen. Secretory IgA represents the first line of defence of the GI mucosa and is central to the normal function of the GI tract as an immune barrier. As the principal immunoglobulin isotype present in mucosal secretions, sIgA plays an important role in controlling intestinal milieu which is constantly presented with potentially harmful antigens such as pathogenic bacteria, parasites, yeast, viruses, abnormal cell antigens, and allergenic proteins. Faecal secretory IgA antibodies exert their function by binding to antigenic epitopes on the invading microorganism, limiting their mobility and adhesion to the epithelium of the mucus membrane. This prevents the antigens from reaching systemic circulation and allowing them to be excreted directly in the faeces.