Calprotectin consists of mammalian proteins S100A8 and S100A9 and is a 24 kDa dimer1. It is secreted during the inflammatory response in the intestinal lumen through leukocyte shedding, active secretion, cell disturbance, and cell death7. Thus, elevated fecal calprotectin levels are correlated with migration of neutrophils into the intestinal mucosa3,4. Clinical applications may include aiding in the diagnosis of ulcerative colitis2, inflammatory bowel diseases (IBD)6, irritable bowel syndrome (IBS)8, and Crohn’s disease5.
This CLIA is designed, developed, and produced for the quantitative measurement of human calprotectin in fecal samples. The assay utilizes a two-site “sandwich” technique with two antibodies that bind to different epitopes of calprotectin.
Assay calibrators, controls, or patient samples are added directly to a reaction vessel containing streptavidin coated magnetic particles. Simultaneously, anacridinium ester antibody and a biotin antibody are added. The magnetic particles capture the biotin antibody as well as an immuno complex in the form of “magnetic particles – biotin calprotectin antibody –calprotectin – acridinium ester calprotectin antibody”.
The materials bound to the solid phase are held in a magnetic field while unbound materials are washed away. Then, the trigger solution is added to the reaction vessel and light emision generated by the reaction is measured with the ECL100 or ECL25 automated CLIA analyzer. The relative light units (RLU) are proportional to the concentration of calprotectin in the sample. The amount of analyte in the sample is determined from a stored, multi-point calibration curve and reported in serum calprotectin concentration.