Calprotectin: time to start testing?

Calprotectin is a heterodimer of calcium-binding proteins released from polymorphic nucleated cells and monocytes upon cellular activation (or death) at sites of active inflammation. It is present in plasma and faeces and said to be highly stable in faeces after collection. The symptoms of functional disorders such as irritable bowel syndrome (IBS) and organic inflammatory bowel disease (IBD) can be very similar, but these are two very different clinical conditions. Recent guidelines from NICE state that faecal calprotectin testing is recommended as an option to support clinicians with the differential diagnosis of IBD or IBS in adults with recent onset lower gastrointestinal symptoms for whom specialist assessment is being considered, if cancer is not suspected, having considered the risk factors (for example, age), and appropriate quality assurance processes and locally agreed care pathways are in place for the testing. This guidance has led to an explosion in requests for calprotectin. Calprotectin is also becoming widely used in monitoring treatment of IBD. A number of methods for measurement of calprotectin are available, including point-of-care tests. However, there are still many problems associated with the assays, particularly the pre-analytical aspects. Moreover, the setting of appropriate cut-off concentrations is still much debated.