Procalcitonin (PCT) is a protein precursor to calcitonin and is 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, as well as other infections leading to sepsis, are current uses for PCT as a biomarker.)
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. Depending on the clinical assessment, a PCT concentration >0.1 ng/mL (reference value <0.05 ng/mL) can indicate clinically relevant bacterial infection.
PCT levels are usually low in viral disorders, chronic inflammatory conditions, or autoimmune conditions.
