Procalcitonin 

Updated: Nov 24, 2015
  • Author: Jiun-Lih Jerry Lin, MBBS, MS(Orth); Chief Editor: Eric B Staros, MD  more...
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Reference Range

Procalcitonin (PCT), a protein that consists of 116 amino acids, is the peptide precursor of calcitonin, a hormone that is synthesized by the parafollicular C cells of the thyroid and involved in calcium homeostasis. Procalcitonin arises from endopeptidase-cleaved preprocalcitonin.

The reference value of procalcitonin in adults and children older than 72 hours is 0.15 ng/mL or less.

Reference values have not been established in infants younger than 72 hours.

In healthy adults, the reference range of procalcitonin is below the level of detection. [1]

The half-life of procalcitonin is 25-30 hours (not significantly altered in individuals with renal dysfunction). [2]

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Interpretation

Conditions associated with mildly elevated serum procalcitonin (PCT) levels (0.15-2 ng/mL) include the following:

Conditions associated with elevated serum procalcitonin levels (>2 ng/mL) include the following:

In neonates aged less than 72 hours, a procalcitonin level of more than 1 ng/mL at birth, 100 ng/mL or more at age 24 hours, and 50 ng/mL or more at age 48 hours suggests serious bacterial infection.

In children with urinary tract infection, a procalcitonin level of more than 0.5 ng/mL suggests renal involvement.

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Collection and Panels

Specifics for procalcitonin (PCT) collection and panels are as follows:

  • Specimen type: Blood serum
  • Container: Vacutainer, red top
  • Collection method: Venipuncture
  • Specimen volume: 0.5 mL

Related tests include complete blood cell (CBC) count, C-reactive protein (CRP), blood culture, and cerebrospinal fluid (CSF) analysis.

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Background

Description

Procalcitonin (PCT), a protein that consists of 116 amino acids, is the peptide precursor of calcitonin, a hormone that is synthesized by the parafollicular C cells of the thyroid and involved in calcium homeostasis. Procalcitonin arises from endopeptidase-cleaved preprocalcitonin.

Procalcitonin is also produced by the neuroendocrine cells of the lung and intestine and is released as an acute-phase reactant in response to inflammatory stimuli, especially those of bacterial origin. This raised procalcitonin level during inflammation is associated with bacterial endotoxin and inflammatory cytokines. [1, 2] Increased levels of serum procalcitonin in response to viral infections and noninfectious inflammatory stimuli such as autoimmune disease and chronic inflammatory processes are much less pronounced, rarely exceeding 0.5 ng/mL. [3, 4] Procalcitonin released as an acute-phase reactant does not result in increased serum calcitonin levels.

The physiological importance and regulation of procalcitonin production is not well understood. Several hypotheses suggest that procalcitonin may be involved in metabolism of calcium, cytokine network, and modulation of nitric oxide (NO) synthesis, as well as pain-relieving effects. [5] No enzymes in the plasma break down procalcitonin. Therefore, if procalcitonin enters the circulation, it remains unchanged, with a half-life of around 30 hours, with no evidence that serum procalcitonin binds to cellular receptors of calcitonin or any specific procalcitonin receptors. [5]

Studies have shown that, in patients with sepsis, higher procalcitonin levels are associated with a greater risk of progression to severe sepsis and septic shock, worsening the survival prognosis. Local bacterial infections and abscesses do not significantly raise procalcitonin levels. [4, 6, 7] Procalcitonin levels fall with successful treatment of severe bacterial infection and severe noninfectious inflammatory stimuli. Persistent or recurrent procalcitonin elevation in the latter setting should prompt suspicion of secondary infection.

Indications/Applications

Indications for serum procalcitonin measurement include the following:

  • To aid in the diagnosis and risk stratification of bacterial sepsis [8, 9]
  • To aid in the diagnosis of renal involvement in children with urinary tract infection
  • To aid in distinguishing bacterial from viral infections, including meningitis [10]
  • To monitor therapeutic response to antibacterial therapy and reduce antibiotic exposure [11, 12, 13, 14, 15]
  • To aid in the diagnosis of systemic secondary infection after surgery and in severe trauma, burns, and multiorgan failure [16]
  • To aid diagnosis of infected necrosis and associated systemic complications in acute pancreatitis [17]

Proposed applications of serum procalcitonin measurement include the following:

  • To aid the choice and timing of the initiation of antibiotic treatment (Procalcitonin Algorithm)
  • To assist with elucidating prognosis of severe localized infections (eg, pneumonia) [18]
  • To aid with elucidating prognosis of critically ill patients with systemic infection
  • Predicting the need of antibiotic treatment in sepsis and to shorten the duration of antibiotics required [19]
  • Use as independent predictor of graft failure late after renal transplantation [20]

Procalcitonin versus C-reactive protein

CRP is the most common laboratory marker used in the clinical setting to evaluate systemic inflammatory response to an infectious agent. It is routinely used as a diagnostic, predictor, and monitoring marker in patients with acute sepsis. Several recent comparison studies have aimed to determine the use of PCT in conjunction with CRP or independent of it in the setting of severe bacterial infections.

Procalcitonin is a more useful diagnostic inflammation parameter than CRP in patients with pediatric neutropenic fever, both in estimating the severity of infection and the duration and origin of the fever. [21]

Procalcitonin is a more reliable parameter than other markers in the diagnosis of bacterial sepsis, allowing better differentiation among sepsis-related fatalities. [22]

Procalcitonin is a useful early diagnostic marker for detection of bacteremia in febrile neutropenia and has better diagnostic value than CRP. [23]

Considerations

Procalcitonin levels may also be elevated in medullary thyroid carcinoma [24] and small-cell lung carcinoma, [24] paralytic/vascular ileus [21] exhibiting paraneoplastic production, and renal failure. [24]

Procalcitonin, although useful in bacterial sepsis, has no value in the assessment of fungal or viral infections and shows no response to intracellular microorganisms (ie, Mycoplasma) or in local infections with no systemic response.

Similar to CRP, clinical conditions associated with high baseline procalcitonin levels include burns, major surgery, and systemic inflammatory processes.

To date, the use of procalcitonin, both as an indicator of severe infection and predictor of antibiotic choices/duration, has been center-specific, with insufficient data from multicenter/multinational studies to support its use as a routine laboratory marker in clinical practice.

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