Calprotectin is a 36 kd calcium and zinc-binding protein released in large quantities from leukocytes, (in particular polymorphonuclear neutrophilic granulocytes (PMN)), into the gut lumen during episodes of intestinal mucosal inflammation. This protein constitutes about 60% of total proteins in the cytoplasm of PMNs and can be reliably quantified in faecal samples to indicate the extent of inflammation.
The concentration of Calprotectin in faeces is correlated with the number of PMNs migrating into the gut lumen and can be measured reliably even in small stool samples (less than one gram). This makes Faecal Calprotectin an exceptionally accurate and convenient marker for investigating bowel inflammation in patients presenting with abdominal symptoms, or monitoring patients with Inflammatory Bowel Disease (IBD).
Organic diseases of the bowel give a strong Calprotectin signal, i.e. elevations are regularly five to several thousand times the upper reference of healthy individuals so in the case of IBD, i.e. ulcerative colitis and Crohn’s disease, the diagnosis can be made earlier by helping clarify the vague symptoms that often accompany the disease. Being a non-invasive test, faecal calprotectin has also been recognised as a useful alternative to endoscopy and biopsy.
Faecal Calprotectin in Primary Care (Diagnosis and referral)
The National Institute for Health and Care Excellence (NICE) in England recommend Faecal Calprotectin testing to help physicians differentiate IBD and non-inflammatory bowel diseases, such as irritable bowel syndrome. This is extremely useful in Primary Care settings where the demand for GP time and resources is high for IBS-like symptoms, particularly in adolescents and young adults. Functional gastrointestinal disorders like irritable bowel syndrome (IBS) do not cause increased faecal Calprotectin concentrations, but organic abdominal disorders like IBD do. Patients with organic and functional gastrointestinal disorders may have similar symptoms, and clinical examination alone may not be sufficient to give a specific diagnosis. A test for faecal Calprotectin is a simple, non-invasive, inexpensive and objective method that can help selecting patients for further investigation such as colonoscopy, or rule out inflammatory bowel diseases with high probability.
In a recent prospective UK study in Primary Care cohort Faecal calprotectin was shown to effectively exclude inflammatory bowel disease symptomatic patients with or without alarm symptoms with a negative predictive value of 98% and 99% respectively. The study estimated that by employing their Faecal Calprotectin Primary Care Pathway and using the IDK Faecal Calprotectin ELISA assay (K6927) to rule our functional gastrointestinal disorders the health care system could save £160 per patient (Aliment Pharmacol Ther. 2018;47:1103–1116).
Faecal Calprotectin in Secondary Care (Monitoring and Management)
As well as contributing to an earlier diagnosis of IBD, Faecal Calprotectin can also be used alongside clinical assessments and therapeutic drug monitoring to monitor the course of disease. It can also be useful for predicting disease outcomes.
Achieving deep remission in IBD is the optimal goal for treatment, and faecal Calprotectin correlates well with disease activity and histological improvement. ?IBD patients in clinical remission with normal C-reactive protein (CRP) levels may still have on-going inflammation, and likewise, CRP levels can be elevated without active luminal disease. In such cases faecal Calprotectin levels offer a truer picture of inflammatory status.
When an individual shows a raised faecal calprotectin they have an increased risk of relapse within a few months, offering a window of opportunity for therapeutic intervention. If mucosal healing can be achieved, the risk of relapse and need for intensified therapeutics or surgery will be reduced.
Normalisation of faecal Calprotectin levels means that the goal of mucosal healing has been achieved.
Monitoring IBD at home with Smart Technology
Recent technological advances have empowered IBD patients by enabling them to self-monitor their faecal calprotectin at home, work, or anywhere in the world whilst remaining connected to their IBD care team via smart apps. QuantOn Cal (KST11002GP) is a Smart phone based IBD app that allows patients with Crohn’s disease or ulcerative colitis to routinely test their stools for faecal calprotectin in the comfort and privacy of their home. The test comprises a rapid test cassette that detects calprotectin in a stool sample and a smart phone app that quantifies the result and transmits it to the patient’s IBD team. This incredible technology has the power to transform the way IBD is managed, enabling the patient to stay in the community, reduce hospital appointments and admissions and free up valuable clinic space in secondary care, all the while being virtually connected to their IBD team.