- Elevation in the serum concentration of procalcitonin (PCT) is associated with systemic infection. This association has led to the proposed use of PCT as a novel biomarker of bacterial sepsis. The advantages and limitations of the American College of Chest Physicians/Society of Critical Care Medicine (ACCP/SCCM) definitions of sepsis are an important consideration that affects the impact of any diagnostic test for sepsis and these issues are discussed. Our main objective is to perform a systematic health technology assessment of PCT as a diagnostic test for sepsis. In an adult intensive care unit (ICU) population, we identify a specific and important question-can PCT accurately distinguish sepsis in patients with systemic inflammatory response syndrome (SIRS) who have a suspected infection? Likelihood ratios are calculated from published data to attempt to find the best answer. The published evidence does not support a general claim that PCT is a useful decision support tool for diagnosing sepsis in patients who have SIRS. Procalcitonin has a slightly better ability to exclude the diagnosis of sepsis. The role for using PCT testing in the ICU will continue to evolve along with our understanding and definition of sepsis.