Procalcitonin, a marker of bacterial infection.

Procalcitonin, the prohormone of calcitonin, is present in high plasma conc entrations in bacterial infections, in the absence of detectable calcitonin , and remains low in viral infection and in inflammatory diseases. Its stab ility and its easy measurement make of procalcitonin a suitable marker of i nfection. During severe infections, the rise of procalcitonin allows to dif ferentiate inflammatory diseases and viral infection with bacterial infecti on in feverish patients. In newborns, the increase induced by bacterial neo natal 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 c hildhood pyelonephritis, procalcitonin is correlated to the importance of r enal scars, as sequelae of infection, but not CRP or cytokines. In patient receiving grafts, procalcitonin allow to differentiate between rejection an d infection. In intensive care patients, PCT has probably a pronostic value of efficacy of antibiotic treatment. Its sensitivity is identical or somet imes superior to that of CRP always superior to that of cytokines at interf eron 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 m echanism in inflammatory cascade. Procalcitonin is an important marker of b acterial infections and its usefulness has to be evaluated by clinicians by comparison with other markers. (C) 2000 Editions scientifiques et medicale s Elsevier SAS.