Abstract
Procalcitonin, a propeptide of calcitonin, is normally produced in the C-cells of the thyroid gland, but it's plasma level markedly increases, mostly due to extra-thyroidal production in cases of severe infections (bacterial, parasitic and fungal) with systemic manifestations, especially in the presence of septic shock. Since noninfectious inflammatory reaction, viral infection and localized bacterial infections manifest only small to modest increases of procalcitonin in plasma, procalcitonin levels may be useful in differentiating between these diseases and sepsis. In addition, it has been suggested that procalcitonin is an early and good marker of elevated cytokines in patients with sepsis, and that it's plasma level is correlated with Sepsis-related Organ Failure Assessment (SOFA) score. On the other hand, traditional markers of infection such as body temperature and white blood cell count are unreliable and often misleading, since they are markers of systemic inflammation which may be noninfectious in origin and therefore non-specific and non-sensitive for sepsis. Although plasma C-reactive protein (CRP) level has been suggested as a good indicator of sepsis and being superior to body temperature and white blood cell count, CRP may increase markedly following severe non-septic systemic inflammatory response syndrome (SIRS) as well as sepsis and thus may not be a good indicator of infection in patients with severe SIRS. Furthermore, plasma CRP level is not correlated with SOFA score. Since plasma procalcitonin is measured easily, quickly and accurately by immunoluminometric assay, it is useful for early diagnosis of sepsis in patients with severe SIRS and as an indicator of severity of sepsis in such patients.
