Interleukin-6 and acute-phase protein concentrations in surgical intensive care unit patients: diagnostic signs in nosocomial infection.

OBJECTIVE

To determine the value of serum concentrations of interleukin-6 (IL-6), C-reactive protein, and glycosylation of alpha 1-acid glycoprotein as tools for diagnosing nosocomial infection in surgical intensive care unit (ICU) patients.

DESIGN

Prospective, consecutive entry study of patients with an anticipated stay of at least 24 hrs in a surgical ICU.

SETTING

University hospital, a major provider of acute surgical care.

PATIENTS

One hundred four consecutive patients admitted to the surgical ICU between March and June 1990.

MEASUREMENTS

Concentrations of IL-6, C-reactive protein, and glycosylation of alpha 1-acid glycoprotein were measured on days 1 and 6 after ICU admission. Clinical evaluation for infection was performed daily in a blinded fashion, i.e., without knowing the results of the acute-phase parameters.

MAIN RESULTS

On day 6 after surgery or trauma, nosocomial infection could be ascertained in 13 cases. The clinical parameter of fever > 38 degrees C had a sensitivity of 54% and a specificity of 90% to demonstrate nosocomial infection. Infected patients showed increased concentrations of IL-6 (p < .001), C-reactive protein (p < .001), and increased reactivity of alpha 1-acid glycoprotein to concanavalin A (p < .001) compared with patients without infections. By choosing appropriate cutoff values, IL-6 determinations had the highest specificity (97%), and C-reactive protein values had the highest sensitivity (85%) for diagnosing nosocomial infections. In uninfected patients, 81% of the IL-6 values, but only 29% of the C-reactive protein values, were back to the normal range on day 6 after injury.

CONCLUSION

Due to the rapid normalization after trauma, a single measurement of the serum IL-6 concentration may be useful to support or refute the clinical suspicion of nosocomial infection.