It was first used in patients with suspected bacterial infections or sepsis to differentiate between infectious and noninfectious causes of systemic inflammatory response syndrome.[25–30] Despite conflicting results on the clinical utility of PCT to reduce antibiotic exposure or predict mortality, it has been adopted into widespread practice in critical care settings and is currently approved by the United States Food and Drug Administration (FDA) for use in patients with suspected sepsis.[27]. This evidence concerns the gene CALCA and bacterial infectious disease.