Procalcitonin, a marker of bacterial infection.

Procalcitonin, the prohormone of calcitonin, is present in high plasma concentrations in bacterial infections, in the absence of detectable calcitonin, and remains low in viral infection and in inflammatory diseases. Its stability and its easy measurement make of procalcitonin a suitable marker of infection. During severe infections, the rise of procalcitonin allows to differentiate inflammatory diseases and viral infection with bacterial infection in feverish patients. In newborns, the increase induced by bacterial neonatal infection is over the physiological rise of procalcitonin during the two first days of life, and PCT appears to be a better maker than CRP or IL-6. In localised bacterial infections, the increase is less important. In childhood pyelonephritis, procalcitonin is correlated to the importance of renal scars, as sequelae of infection, but not CRP or cytokines. In patient receiving grafts, procalcitonin allow to differentiate between rejection and infection. In intensive care patients, PCT has probably a pronostic value of efficacy of antibiotic treatment. Its sensitivity is identical or sometimes superior to that of CRP always superior to that of cytokines at interferon alpha. Its specificity is always superior to that of CRP and cytokines. Further studies are needed to determine the exact origin of PCT and the mechanism in inflammatory cascade. Procalcitonin is an important marker of bacterial infections and its usefulness has to be evaluated by clinicians by comparison with other markers. (C) 2000 Editions scientifiques et medicales Elsevier SAS.