Procalcitonin used as a marker of infection in the intensive care unit

OBJECTIVE: To determine the value of procalcitonin (ProCT) as a marker of infection in critically ill patients. DESIGN: Prospective, observational study. SETTING: Medicosurgical department of intensive care (31 beds). PATIENTS: One hundred eleven infected and 79 noninfected patients. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: ProCT and C-reactive protein (CRP) concentrations were monitored daily. The best cutoff values for ProCT and CRP were 0.6 ng/mL and 7.9 mg/dL, respectively. Compared with CRP, ProCT had a lower sensitivity (67.6 vs. 71.8), specificity (61.3 vs. 66.6), and area under the receiver operating characteristic curve (0.66 vs. 0.78, p < .05). The combination of ProCT and CRP increased the specificity for infection to 82.3%. In the infected patients, plasma ProCT, but not CRP, values were higher in nonsurvivors than in survivors. Infected patients with bacteremia had higher ProCT concentrations than those without bacteremia, but similar CRP concentrations. ProCT levels were particularly high in septic shock patients. CONCLUSIONS: ProCT is not a better marker of infection than CRP in critically ill patients, but it can represent a useful adjunctive parameter to identify infection and is a useful marker of the severity of infection.