The CRP controls are trueness controls for C-reactive protein. They are stable human serum-based liquid controls used to monitor analytical conditions in CRP determinations. CRP Controls Duotrol® CRP-Qualitätskontrollen are available in seven different concentration ranges (7 levels) to provide an accurate estimate of an individual patient’s increase in CRP concentration. In the context of acute inflammation, CRP in the blood usually increases 10- to 100-fold within a few hours, depending on the severity of the inflammation. The most significant increase occurs in bacterial infections. In chronic inflammations, there is a permanent, less pronounced activation of CRP.