Procalcitonin (PCT) is a protein precursor to calcitonin produced in the thyroid.
PCT increases early in infection and has greater specificity for infection than CRP. Increased PCT can be observed within 3–6 hours of infection. Acute low respiratory infections and other infections leading to sepsis are currently used as biomarkers for PCT.
PCT enables the differentiation between a severe bacterial infection and other clinical conditions that may be causing a systemic inflammatory response, allowing antibiotic treatment to begin sooner. Elevated PCT values generally correlate well with positive blood and other culture results. A PCT concentration >0.1 ng/mL (reference value <0.05 ng/mL) can indicate clinically relevant bacterial infection depending on the clinical assessment.
PCT levels are usually low in viral disorders, chronic inflammatory, or autoimmune conditions.
