Procalcitonin as a biomarker in respiratory tract infection

Serum procalcitonin (PCT) levels rapidly increase in patients with invasive bacterial disease. PCT levels increase faster than do C-reactive protein levels. Furthermore, a rapid decrease in the PCT level is supporting evidence that the source of the bacterial infection is responding to clinical management. In patients with community-acquired bacterial pneumonia, sequential PCT levels are useful as a guide to shorter courses of antimicrobial therapy. With use of emerging multiplex real–time polymerase chain reaction platforms for the detection of viral and bacterial respiratory pathogens, it should be possible to critically assess whether an elevated serum PCT level is a valid biomarker of invasive bacterial infection. Serum procalcitonin (PCT) levels are of interest as a biomarker in patients with respiratory tract in-fections for several reasons. Serum PCT levels are el-evated in patients with bacterial pneumonia and septic shock [1, 2]. To the contrary, data suggest that serum PCT levels are not elevated in patients with viral re-spiratory tract infection unless there is a super