Interpretation

Systemic inflammatory response syndrome, sepsis, severe sepsis, and septic shock were categorized according to the criteria of the consensus conference of the American College of Chest Physicians/Society of Critical Care Medicine.(1)

The change of procalcitonin (PCT) concentration over time provides prognostic information about the risk of mortality(2) within 28 days for patients diagnosed with severe sepsis or septic shock coming from the emergency department, intensive care unit, other medical wards, or directly from outside the hospital. Data support the use of procalcitonin determinations from the day severe sepsis or septic shock is first diagnosed (day 0) or the day thereafter (day 1) and the fourth day after diagnosis (day 4) for the classification of patients into higher and lower risk for mortality within 28 days.

Change in procalcitonin of 80% or less:

A decrease of PCT levels below or equal to 80% defines a positive change in PCT test result representing a higher risk for 28-day all-cause mortality of patients diagnosed with severe sepsis or septic shock.

Change in procalcitonin above 80%:

A decrease of PCT levels of more than 80% defines a negative change in PCT result representing a lower risk for 28-day all-cause mortality of patients diagnosed with severe sepsis or septic shock.

Positive results:

Procalcitonin greater than or equal to 0.25 ng/mL may indicate bacteremia or bacterial pneumonia; however, it is a non-specific biomarker. False positives can be seen in patients with a variety of illnesses, including but not limited to severe trauma, shock, recent surgery, burns, renal insufficiency, severe liver disease, COVID-19, and certain malignancies.

Negative results:

Procalcitonin less than 0.25 ng/mL may indicate lower probability of bacteremia or bacterial pneumonia. Intracellular bacteria, viruses, and fungi do not cause elevation of procalcitonin, so low values (<0.25 ng/mL) do not rule out other infections.