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Separate serum from the blood within 60 minutes of venipuncture. Serum specimen must be clear and free of red cells, particulate matter including fibrins which interferes with the assay. Specimens containing free red cells, particulate matter including fibrins should be re-centrifuged. Frozen specimens should be brought to room temperature and re-centrifuged to get a clear specimen.
Outreach specimens should be sent frozen. Three freeze and thaw cycles are acceptable.
> 48 hours
Stable up to 6 months
Procalcitonin (PCT), a prohormone of calcitonin, is secreted by a variety of cell types in response to proinflammatory stimulation, specifically when bacterial in nature. Detection and monitoring of elevated PCT levels is thus useful in the setting of significant bacterial infections such as bacterial sepsis and pneumonia. This quantitative test is cleared by the FDA as an aid in the risk assessment of critically ill patients on their first day of ICU admission for progression to bacterial severe sepsis and septic shock. Published studies have also found the PCT assay to be useful in the diagnosis of other severe bacterial infections.
The interpretation of a PCT level depends on the nature of the suspected bacterial infection, and must be made in the context of clinical signs and symptoms and the results of other diagnostic studies. Generally speaking, a PCT level of < 0.10ng/mL confidently rules out a significant local or systemic bacterial infection in patients >72 hours in age, while a value >2.00ng/mL is highly supportive of bacterial sepsis and/or septic shock. Depending on the circumstances, a PCT value >0.50ng/mL is supportive of a significant bacterial infection when consistent with clinical signs and other diagnostic studies. (See below for specific interpretations.*)
The interpretation of neonatal PCT levels is more complex, since PCT levels in healthy neonates is low at birth, rises as much as 20-fold by 24 hours of age, and then drops into the adult reference range by 72 hours of age. (See graph: Procalcitonin (PCT) Levels in the Neonate)
Neonates 0-72 hours: (See graph: Procalcitonin (PCT) Levels in the Neonate)
Neonates >72 hours-adults: <0.05 - 0.10 ng/mL
Age: 0-72 hoursPCT value: AnyInterpretation: In the absence of bacterial infection, procalcitonin values begin to rise immediately at birth, peak at Day 2, and then fall to adult levels (0.0-0.1ng/mL) by Day 3 of life. Nevertheless, neonatal PCT levels predictably rise above the baseline in response to severe bacterial infections. (See graph: Procalcitonin (PCT) Levels in the Neonate)Also refer to C. Chiesa et al, 1998. Reliability of procalcitonin concentrations for the diagnosis of sepsis in critically ill neonates. Clin. Infect. Dis. 26:664.)