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

TLDR

Diagnosing infection in critically ill patients is difficult because conventional markers are unreliable, and although calcitonin precursors rise during infection, their diagnostic accuracy for sepsis in an unselected medical ICU population is unknown. The study aimed to compare the diagnostic utility of serum calcitonin precursors, C‑reactive protein, interleukin‑6, and lactate for sepsis in consecutive medical ICU patients. In a prospective cohort of 101 ICU patients, blood samples were taken at multiple time points and patients were daily reclassified for SIRS, sepsis, severe sepsis, or septic shock using standardized criteria, blind to the biomarker levels. Calcitonin precursors were the most reliable marker, with concentrations >1 ng/mL yielding 89 % sensitivity and 94 % specificity for sepsis, outperforming CRP, IL‑6, and lactate, and high levels were linked to poorer prognosis.

Abstract

The diagnosis of infection in critically ill patients is challenging because traditional markers of infection are often misleading. For example, serum concentrations of calcitonin precursors are increased in patients with infections. However, their predictive accuracy for the diagnosis of sepsis in unselected patients in a medical intensive care unit (ICU) is unknown. Therefore, we compared the usefulness of serum concentrations of calcitonin 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 > or =24 hrs in a medical ICU.Prospective cohort study.Medical intensive care unit in a university medical center.101 consecutive critically ill patients.None.Blood samples were collected at various time points during the course of the disease. Systemic inflammatory response syndrome, 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 interleukin-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 of variance). In a receiver operating characteristic curve analysis, calcitonin precursors were found to be the most reliable laboratory variable for the diagnosis of sepsis as compared with C-reactive protein, interleukin-6, and lactate (p < .01, for each comparison). Calcitonin precursor concentrations of >1 ng/mL had sensitivity of 89% and specificity of 94% for the diagnosis of sepsis. High serum concentrations of calcitonin precursors were associated with poor prognosis (p = .01).In a medical ICU, serum calcitonin precursor concentrations are more sensitive and are specific markers of sepsis as compared with serum C-reactive protein, interleukin-6, and lactate levels.