Procalcitonine, is a protein made up of 116 aminoacids. It is the precursor of actie calcitonine with 32 aminoacids. In normal metabolic conditions, hormonally active calcitonine is synthesized and secreted from procalcitonine via intacellular proteolitical dissociation, in the C cells of thyroid. In severe bacterial infections and sepsis, intact procalcitonine too is detected in the blood.

Procalcitonine is a very stable molecule with its 20-24 hours half-life. Since its also stable in vitro, it does not necessitate special conditions during pre-analysis sample collection or storage. Precalcitonine starts increasing 2-3 hours following its induction via endotoxins, and may reach extremely high levels in septical shock and severe sepsis. The values decrease as a response to successful treatment. Increasing values despite the treatment, or persistant high levels indicate a bad prognosis.

Procalcitonine is a very specific and new indicator for severe bacterial infections and sepsis diagnosis. Procalcitonine measurements reduces the antibiotics use in treatments. Because antibiotics use is not suggested until certain limits are exceeded.