Diagnostic value of procalcitonin for bacterial infection in elderly patients in the emergency department.

OBJECTIVES: To evaluate the diagnostic performance of procalcitonin (PCT) in elderly patients with bacterial infection in the emergency department (ED).

DESIGN: Prospective.

SETTING: ED of a tertiary care hospital.

PARTICIPANTS: Elderly patients with systemic inflammatory response syndrome (SIRS) enrolled from September 2004 through August 2005.

MEASUREMENTS: A serum sample for the measurement of PCT, two sets of blood cultures, and other cultures of relevant specimens from infection sites were collected in the ED. Two independent experts blinded to the PCT results classified the patients into bacterial infection and nonbacterial infection groups.

RESULTS: Of the 262 patients with SIRS enrolled, 204 were classified as having bacterial infection and 48 as having bacteremia. PCT levels were significantly higher in patients with bacteremia than in those without. The area under the receiver operating characteristic curve for identification of bacteremia according to PCT was 0.817 for the old-old group (>or=75), significantly higher than 0.639 for the young-old group (65-74); P=.02). The diagnostic sensitivity, specificity, positive predictive value, and negative predictive value of PCT for bacteremia in patients aged 75 and older were 96.0%, 68.3%, 33.8%, and 98.8%, respectively, with a PCT cutoff value of 0.38 ng/mL.

CONCLUSION: PCT is sensitive for diagnosing bacteremia in elderly patients with SIRS at ED admission but is helpful in excluding bacteremia only in those aged 75 and older. PCT is not an independent predictor of local infections in these patients.