CRP versus white blood cell count (WBC) |
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"Acute-phase reaction" is a collective designation for changes in serum protein profile and cellular immune
response, encompassing symptoms like fever tiredness and general malaise induced by infection, inflammation or trauma. Serum proteins that are upregulated or downregulated during inflammation are called positive or negative acute-phase proteins, respectively.
CRP - The most valuable acute-phase protein
At the moment, CRP is the best known and diagnostically most valuable acute-phase protein. The
group of acute-phase proteins includes besides CRP many other proteins, such as serum amyloid A (SAA),
fibrinogen, procalcitonin, haptoglobin, alpha2- haptoglobin, alpha1-acid glycoprotein, caeruloplasmin,
alpha1-antitrypsin and albumin. The disadvantage of haptoglobin (see Fig. 4), alpha2-haptoglobin, alpha1-
acid glycoprotein, caeruloplasmin, alpha1-antitrypsin and albumin is that the differences between normal
and pathological values are very small. The values measured in pathological conditions are only a few
times those found in healthy individuals, and they are also determined by other (e.g. nutritional) factors in
addition to infections.
The concentration of CRP in serum reflects the rate of synthesis of this protein in the liver. Hepatocyte CRP
synthesis is triggered by cytokines such as interleukin-6 (IL-6), interleukin-1 (IL-1) and tumour necrosis factor
(TNF) secreted by monocytes/macrophages. The elevation of IL-6 concentration in serum is one of the earliest markers
of inflammatory processes, detectable 2-3 h after onset of infection. Similarly, IL-6 concentration decreases very
rapidly, almost too rapidly to be detected, to normal. Rise in CRP concentration is normally detectable 4-7 h later,
depending on the sensitivity of assay. CRP both rises and decreases rapidly according to inflammation activity,
which makes it a very suitable marker for detecting inflammation.
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