Assessment of procalcitonin as a diagnostic marker of underlying infection in patients with febrile neutropenia.

The novel inflammatory marker procalcitonin (PCT) was assessed as an index of infection in patients with febrile neutropenia. Blood samples were obtained from 115 patients with febrile neutropenia for determination of PCT levels before onset of fever and daily until the resolution of fever. The median PCT level on the first day of fever was 8.23 ng/mL in patients with bacteremia, compared with 0.86 ng/mL in patients with localized bacterial infections (P=.017). The median PCT level on the first day of fever was 2.62 ng/mL in patients with severe sepsis, compared with 0.57 ng/mL in patients with clinically localized infections (P<.001). A dramatic decrease in PCT levels was documented after resolution of the infection; PCT levels were elevated when the infection worsened. Pronounced PCT levels were also found in patients with fever of unknown origin who were responding to antimicrobial chemotherapy, compared with those not responding to treatment with antibiotics. PCT levels were particularly elevated in patients with bacteremia and severe sepsis. These findings provide new insight into the application of PCT in clinical trials as a diagnostic tool of the severity of an infection in patients with febrile neutropenia and of the need to change antimicrobial regimen.