Procalcitonin Test (PCT): is a blood test performed often if there is a suspicion of bacterial sepsis, a severe systemic infection that can become life-threatening. The procalcitonin test is an easy way to make the diagnosis quickly and potentially save lives. Procalcitonin is a peptide naturally produced in the body that serves as a marker for sepsis. It is important to note that procalcitonin does not diagnose a type of infection; rather, it is a strong indicator of an infection.