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(prō-kal″sĭ-tō′nĭn) [ pro- + calcitonin],


A polypeptide produced within C cells in the thyroid gland. It is composed of 116 amino acids and has a molecular weight of 13 kD. Cleavage of the molecule liberates calcitonin. In severe bacterial infections, procalcitonin is released from the thyroid into the blood. Laboratory tests for the molecule can help distinguish bacterial infections from viral infections.
Medical Dictionary, © 2009 Farlex and Partners


Synonym/acronym: PCT.

Common use

To assist in diagnosing bacterial infection and risk for developing sepsis.


Serum (2 mL) collected in a gold-, red-, or red/gray-top tube. Plasma (2 mL) collected in a lavender-top (EDTA) or a green-top (lithium or sodium heparin) tube is also acceptable.

Normal findings

(Method: Fluorescence immunoassay)
AgeConventional UnitsSI Units (Conventional Units × 1)
NewbornLess than 2 ng/mLLess than 2 mcg/L
18–20 hrLess than 20 ng/mLLess than 20 mcg/L
48 hrLess than 5 ng/mLLess than 5 mcg/L
3 days–adultLess than 0.1 ng/mLLess than 0.1 mcg/L
Interpretive Guidelines
InterpretationConventional UnitsSI Units
Bacterial infection absent or very unlikelyLess than 0.1 ng/mLLess than 0.1 mcg/L
Bacterial infection possible; low risk for development of sepsisLess than 0.5 ng/mLLess than 0.5 mcg/L
Interpretive Guidelines
InterpretationConventional UnitsSI Units
Bacterial infection likely; development of sepsis is possible0.5–2 ng/mL0.5–2 mcg/L
Bacterial infection very likely; high risk for development of sepsis2.1–9.9 ng/mL or greater2.1–9.9 mcg/L or greater
Bacterial infection severe; septic shock is probable10 ng/mL or greater10 mcg/L or greater


Sepsis is a very serious, potentially life-threatening systemic inflammatory response to infection. The host inflammatory reaction was termed systemic inflammatory response syndrome (SIRS) by the American College of Chest Physicians and the Society of Critical Care Medicine in 1992. SIRS is defined by documented clinical evidence of bacterial infection (e.g., culture results) in the presence of two of four other criteria: temperature greater than 100.4°F or less than 96.8°F, heart rate greater than 90 beats/min, hyperventilation (greater than 20 breaths/minute or Paco2 less than 32 mm Hg), or white blood cell (WBC) count greater than 12 × 103/microL or less than 4 × 103/microL. The development of sepsis is initiated by the activation of circulating macrophages resulting from binding to receptors on the outer membrane of gram-negative or gram-positive bacteria. Other organisms, such as fungi, parasites, and viruses, are also capable of initiating SIRS, which can develop into sepsis. Severe sepsis involves a systemic inflammatory response that suppresses the immune system, activation of the coagulation process (reflected by prolonged PT and aPTT, elevated d-dimer, and deficiency of protein C), cardiovascular insufficiency, and multiple organ failure. The incidence of sepsis in hospitals is especially high in noncardiac intensive care units. Early-onset neonatal sepsis occurs in the first 72 hours of life with 85% of cases presenting in the first 24 hours. Early-onset neonatal sepsis is the result of colonization of the neonate from the mother as it moved through the birth canal before delivery. The Centers for Disease Control and Prevention recommends universal screening for group B Streptococcus for all pregnant women at 35 to 37 weeks’ gestation. Other organisms associated with early-onset neonatal sepsis include coagulase-negative Staphylococcus, Escherichia coli, Haemophilus influenzae, and Listeria monocytogenes.

Late-onset neonatal sepsis, during days 4 to 90, is acquired from the environment and has been associated with infection by Acinetobacter, Candida, coagulase-negative Staphylococci, Enterobacter, E. coli, group B Streptococcus, Klebsiella, Pseudomonas, Serratia, and Staphylococcus aureus, as well as some anaerobes. Normally procalcitonin, the precursor of the hormone calcitonin, is produced by the C cells of the thyroid. In SIRS, microbial toxins and inflammatory mediator proteins, including cytokines, tumor necrosis factor α, interleukin 1, prostaglandins, and platelet activating factor, may trigger the production of large amounts of procalcitonin by nonthyroidal, non-neuroendocrine cells throughout the body. Each phase of the inflammatory response creates another cascade of events that may conclude with septic shock and death. Procalcitonin is detectable within 2 to 4 hr after an SIRS-initiating event and peaks within 12 to 24 hr. Serial measurements are useful to monitor patients at risk of developing sepsis or to monitor response to therapy.

This procedure is contraindicated for



  • Assist in the diagnosis of bacteremia and septicemia
  • Assist in the differential diagnosis of bacterial versus viral meningitis
  • Assist in the differential diagnosis of community-acquired bacterial versus viral pneumonia
  • Monitor response to antibacterial therapy

Potential diagnosis

Increased in

  • Bacteremia or septicemia (related to SIRS induced overproduction of procalcitonin)
  • Major surgery (related to inflammation in the absence of sepsis)
  • Multiorgan failure (related to inflammation in the absence of sepsis)
  • Neuroendocrine tumors (medullary thyroid cancer, small-cell lung cancer, and carcinoid tumors) (related to procalcitonin [PCT]-secreting tumor cells)
  • Severe burns (related to inflammation in the absence of sepsis)
  • Severe trauma (related to inflammation in the absence of sepsis)
  • Treatment with OKT3 antibodies (antibody used to protect a transplanted organ or graft from attack by T cells and subsequent rejection) and other drugs that stimulate the release of cytokines (related to inflammatory response in the absence of sepsis)

Decreased in


Critical findings


Interfering factors


Nursing Implications and Procedure


  • Positively identify the patient using at least two unique identifiers before providing care, treatment, or services.
  • Patient Teaching: Inform the patient this test can assist in assessing for infection and response to antibiotic treatment.
  • Obtain a history of the patient’s complaints, including a list of known allergens, especially allergies or sensitivities to latex. The patient may complain of pain related to the inflammatory process in connective or other tissues.
  • Obtain a history of the patient’s immune system, symptoms, and results of previously performed laboratory tests and diagnostic and surgical procedures.
  • Obtain a list of the patient’s current medications, including herbs, nutritional supplements, and nutraceuticals (see Effects of Natural Products on Laboratory Values online at DavisPlus).
  • Review the procedure with the patient. Inform the patient that specimen collection takes approximately 5 to 10 min. Address concerns about pain and explain that there may be some discomfort during the venipuncture.
  • Sensitivity to social and cultural issues, as well as concern for modesty, is important in providing psychological support before, during, and after the procedure.
  • Note that there are no food, fluid, or medication restrictions unless by medical direction.


  • Potential complications: N/A
  • Avoid the use of equipment containing latex if the patient has a history of allergic reaction to latex.
  • Instruct the patient to cooperate fully and to follow directions. Direct the patient to breathe normally and to avoid unnecessary movement.
  • Observe standard precautions, and follow the general guidelines in Patient Preparation and Specimen Collection. Positively identify the patient, and label the appropriate specimen container with the corresponding patient demographics, initials of the person collecting the specimen, date, and time of collection. Perform a venipuncture.
  • Remove the needle and apply direct pressure with dry gauze to stop bleeding. Observe/assess venipuncture site for bleeding or hematoma formation and secure gauze with adhesive bandage.
  • Promptly transport the specimen to the laboratory for processing and analysis.


  • Inform the patient that a report of the results will be made available to the requesting health-care provider (HCP), who will discuss the results with the patient.
  • Answer any questions or address any concerns voiced by the patient or family.
  • Depending on the results of this procedure, additional testing may be performed to evaluate or monitor progression of the disease process and determine the need for a change in therapy. Evaluate test results in relation to the patient’s symptoms and other tests performed.

Related Monographs

  • Related tests include ALKP, ALT, AST, antimicrobial drugs, bilirubin total and fractions, coagulation factors, CBC, CBC platelet count, CBC WBC count and differential, creatinine, CRP, culture bacterial blood, culture bacterial anal/genital, culture bacterial urine, ESR, Gram stain, lactic acid, aPTT, PT, and Protein C.
  • Refer to the Immune System table at the end of the book for related tests by body system.
Handbook of Laboratory and Diagnostic Tests, © 2013 Farlex and Partners
References in periodicals archive ?
The role of procalcitonin as a guide for the diagnosis, prognosis, and decision of antibiotic therapy for lower respiratory tract infections.
Similarly, in a recent systematic review by Acharya et al., the pooled sensitivity and specificity of procalcitonin for diagnosing acute appendicitis have been found as 36% and 88%, respectively, and for diagnosing perforated appendicitis as 69% and 67%, respectively (13).
(20) conducted their study with adults and reported that in severe CAP sepsis situations, high DD levels are important for an early diagnosis; DD, procalcitonin and CRP levels are correlated with each other.
In conclusion, procalcitonin testing is used in our burns unit as an early indicator of sepsis, toxic shock syndromes, monitoring response and stewardship to antimicrobial therapy.
The combination of procalcitonin and CRP outperformed a multitude of other two-, three-, and four-biomarker combinations tested, with an area under the curve of 93% for combined sensitivity and specificity.
Ability of procalcitonin to discriminate infection from non-infective inflammation using two pleural disease settings.
The researchers found that the treating physician received procalcitonin assay results for 95.9 and 2.2 percent of patients in the procalcitonin and usual care groups, respectively.
Procalcitonin in bacterial infections - Hype, hope, more or less?
Decreases in procalcitonin and C-reactive protein are strong predictors of survival in ventilator-associated pneumonia.
Patients with conditions associated with high procalcitonin levels, such as active infection, thyroid disease, renal failure, chronic liver or intestinal disease, and chronic obstructive pulmonary disease, were also excluded.
Use of antibiotic in conditions where no infectious disease is found or a viral infection is found when clinical findings, laboratory variables (white blood cell count, neutrophil count, CRP and procalcitonin value), lung imaging, and culture results are evaluated