Calcitonin precursors are reliable markers of sepsis in a medical intensive care unit

Objective: The diagnosis of infection in critically ill patients is challen ging because traditional markers of infection are often misleading. For exa mple, serum concentrations of calcitonin precursors are increased in patien ts with infections. However, their predictive accuracy for the diagnosis of sepsis in unselected patients in a medical intensive care unit (ICU) is un known. Therefore, we compared the usefulness of serum concentrations of cal citonin precursors, C-reactive protein, interleukin-6, and lactate for the diagnosis of sepsis in consecutive patients suffering from a broad range of diseases with an anticipated stay of greater than or equal to 24 hrs in a medical ICU. Design: Prospective cohort study. Setting: Medical intensive care unit in a university medical center, Patien ts: 101 consecutive critically ill patients. Intervention: None. Measurements and Main Results: Blood samples were collected at various time points during the course of the disease. Systemic inflammatory response sy ndrome, sepsis, severe sepsis, and septic shock were diagnosed according to standardized criteria, and patients were reclassified daily without prior knowledge of the serum concentrations of calcitonin precursors or interleuk in-6. At admission, 99% of the patients had systemic inflammatory response syndrome, 53% had sepsis, and 5% developed sepsis during their stay in the ICU. Calcitonin precursors, C-reactive protein, interleukin-6, and lactate levels increased with the severity of infection (p <.01, one-way analysis o f variance). In a receiver operating characteristic curve analysis, calcito nin precursors were found to be the most reliable laboratory variable for t he diagnosis of sepsis as compared with C-reactive protein, interleukin-6, and lactate (p <.01, for each comparison). Calcitonin precursor concentrati ons of >1 ng/mL had sensitivity of 89% and specificity of 94% for the diagn osis of sepsis. High serum concentrations of calcitonin precursors were ass ociated with poor prognosis (p =.01). Conclusions: In a medical ICU, serum calcitonin precursor concentrations ar e more sensitive and are specific markers of sepsis as compared with serum C-reactive protein, interleukin-6, and lactate levels.