Clinical biochemistry

Reference range

S_CRP  < 8mg/L

S_PCT  < 0,1 µg/L

Laboratory markers of inflammatory conditions are based on the production of effectors in response to the pathogen. In addition to blood counts (leukocytosis, neutrophilic granulocytes, left shift), we most commonly use the determination of C-reactive protein (CRP) and procalcitonin (PCT). Both respond to the presence of Pathogen Associated Molecular Patterns (PAMPs), which are recognized by macrophages. In response to this stimulus, macrophages trigger, among other things, the synthesis of interleukin 6 (Il-6) - which stimulates the synthesis of PCT in many tissues (but mainly in the liver) and CRP in the liver and adipocytes. The advantage of PCT over CRP is a slightly earlier rise and a more pronounced response to the retreat of infection. CRP rises in bacterial as well as viral (less), mycotic, allergic and autoimmune inflammation. The decision point for distinguishing between viral and bacterial inflammation is around 50 mg/L. CRP is also a general marker of tissue breakdown - it rises after surgery, trauma, in tumors. PCT is slightly more specific for bacterial and mycotic inflammation, and among non-infectious increases, name severe burns, severe trauma, major surgery, and multi-organ failure. We consider values of < 0.5 µg/L to be low; values at 2 µg/L can be used as an aid in the diagnosis of sepsis. PCT is a useful biomarker to help in the decision to deploy and withdraw antibiotic therapy.