S100A8, S100A9, S100A9dm and S100A9tr. S100At is the total concentration of detected calprotectin isoforms.
Synonym: S100A8/9 or MRP8/14.
Method(s): MALDI-TOF MS (1).
Calprotectin belongs to the S100 family of Ca-binding proteins and represents different hetero-complexes of S100A8, S100A9 and an isoform of truncated S100A9. The definition of the calprotectin hetero-complex is not consistent in the literature. The hetero-dimer has a molecular mass of about 24kDa. Binding of calcium and zinc determines the conformation, stability and function of the complexes. Calprotectin is highly expressed in neutrophils and other cells, and is classified as Damage Associated Molecular Pattern (DAMP) and interacting with TLR4 and possibly RAGE. While faecal calprotectin is widely used to diagnose inflammatory bowel diseases, quantification of calprotectin in serum or EDTA-plasma has recently become increasingly important for investigation of various inflammatory diseases as well as different types of cancers (2,3).
Assessment of inflammation.
Matrix: Serum, but preferably EDTA-plasma (2). See also stability curves for calprotectin.
Volume: Minimum volume is 30 µL, but 100 µL is optimal and allows reanalysis.
Preparation: The blood sample must be centrifuged and the plasma/serum fraction put on ice, and frozen.
Samples may be stored at 2-8 °C for up to 30 days and are stable at -20°C for at least 6 months.
Reported values: 0-30 µg/ml.
Intraclass correlation coefficient (ICC): 0.3-0.5.
1. Gao, J., Meyer, K., Borucki, K., and Ueland, P.M. (2018). Multiplex immuno-MALDI-TOF MS for targeted quantification of protein biomarkers and their proteoforms related to inflammation and renal dysfunction. Anal Chem 90, 3366-373.
2. Pruenster, M., Vogl, T., Roth, J., and Sperandio, M. (2016). S100A8/A9: From basic science to clinical application. Pharmacol Ther 167, 120-131.
3. Nordal, H.H., Fagerhol, M.K., Halse, A.K., and Hammer, H.B. (2018). Calprotectin (S100A8/A9) should preferably be measured in EDTA-plasma; results from a longitudinal study of patients with rheumatoid arthritis. Scand J Clin Lab Invest 78, 102-08.