Procalcitonin as a marker of the systemic inflammatory response to infection

Despite advances in the diagnosis and treatment of infections diseases, sepsis and ensuing multiorgan failure are the major causes of morbidity and mortality in the intensive care units. Such manifestations of systemic inflammation as fever, leukocytosis, tachycardia, etc. may be noninfectious in origin and are neither specific nor sensitive for sepsis. Procalcitonin is a new potential marker for detection of bacterial, fungal and protozoal infections. Procalcitonin, a propeptide of calcitonin, is normally produced in the C-cells of the thyroid gland. Procalcitonin is a polypeptide consisting of 116 amino acids and with a molecular weight of about 13 kDa. During severe systemic infections it is produced by extrathyroidal tissues. Procalcitonin can be put to immediate use in both diagnostic and therapeutic decision-making. This review article discusses biology of procalcitonin, its laboratory determination, usage as an indicator for severe infection and sepsis, and comparison with circulating cytokines in severe infection. It also reviews value of procalcitonin in differentiation of infectious vs non-infectious inflammatory host response, possible elevation of procalcitonin in the absence of infection, its use for differentiation of viral and non-viral infections and as marker for prognosis and evaluation of therapy. Specific indications for determination of procalcitonin are also discussed