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 alpha1-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 alpha1-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 alpha1-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.