Procalcitonin

Test ID: 

706304

CPT code:

84145

Synonyms:

•PCT

Clinical Use:

Used in conjunction with other laboratory findings and clinical assessments, Elecsys BRAHMS PCT is intended for use as follows11:

• to aid in the risk assessment of critically ill patients on their first day of ICU admission for progression to severe sepsis and septic shock;

• to determine the change in PCT level over time as an aid in assessing the cumulative 28-day risk of all-cause mortality for patients diagnosed with severe sepsis or septic shock in the ICU or when obtained in the emergency department or other medical wards prior to ICU admission;

• to aid in decision making on antibiotic therapy, for inpatients or patients in the emergency department with suspected or confirmed lower respiratory tract infections (LRTI) — defined as community-acquired pneumonia (CAP), acute bronchitis, and acute exacerbation of chronic obstructive pulmonary disease (AECOPD);

• to aid in decision making on antibiotic discontinuation for patients with suspected or confirmed sepsis.

Additional Information:

PCT is the prohormone of the hormone calcitonin, but PCT and calcitonin are distinct proteins. Calcitonin is exclusively produced by C-cells of the thyroid gland in response to hormonal stimuli, whereas PCT can be produced by several cell types and many organs in response to proinflammatory stimuli, in particular by bacterial products.1

In healthy people, plasma PCT concentrations are found to be below 0.1 μg/L.2 Depending on the clinical background, a PCT concentration above 0.1 μg/L can indicate clinically relevant bacterial infection, requiring antibiotic treatment.3 PCT levels rise rapidly (within 6 to 12 hours) after a bacterial infectious insult with systemic consequences. The magnitude of the increase in PCT concentration correlates with the severity of the bacterial infection.4 At a PCT concentration >0.5 μg/L, a patient should be considered at risk of developing severe sepsis or septic shock.5,6 On the other hand, the relief of the septic infection is accompanied by a decrease in the PCT concentration which returns to normal with a half-life of 24 hours,7,8 (ie, the continuous decline of PCT is indicative of effective source control measures and has been implicated in the safe deëscalation of antibiotic therapy).9,10

Data support the following interpretative risk assessment criteria

PCT > 2 ng/mL: A PCT level above 2.0 ng/mL on the first day of ICU admission is associated with a high risk for progression to severe sepsis and/or septic shock.

PCT < 0.5 ng/mL: A PCT level below 0.5 ng/mL on the first day of ICU admission is associated with a low risk for progression to severe sepsis and/or septic shock.

Note: Concentrations < 0.5 ng/mL do not exclude an infection, on account of localized infections (without systemic signs) which can be associated with such low concentrations, or a systemic infection in its initial stages (< 6 hours).

Furthermore, increased procalcitonin can occur without infection. PCT concentrations between 0.5 and 2.0 ng/mL should be interpreted taking into account the patient’s history. It is recommended to retest PCT within 6-24 hours if any concentrations < 2 ng/mL are obtained.

The change of PCT concentration over time (Delta PCT) provides prognostic information about the risk of mortality within 28 days for patients diagnosed with severe sepsis or septic shock coming from the emergency department, ICU, other medical wards, or directly from outside the hospital. Data support the use of PCT 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. The Delta PCT is calculated in the manufacturer’s package insert for the Elecsys BRAHMS PCT as:

The change in PCT (Day 0 value minus Day 4 value) divided by the Day 0 value, all multiplied by 100%.

This calculated result is interpreted as follows:

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

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

Notes:

• If Day 0 result is not available, Day 1 result may be used.

• If more than one PCT value is available on Day 0 (or Day 1), enter the highest value.

• If more than one PCT value is available on Day 4, enter the most recent value.

Specimen Type:

Serum or plasma, frozen

Requested Volume: 

0.8 mL

Minimum Volume: 

0.5 mL

Container Type: 

Red-top tube, gel-barrier tube, green-top (lithium heparin) tube, or lavender-top (EDTA) tube

Collection:

Separate serum or plasma from cells and transfer to a plastic transport tube before freezing. To avoid delays in turnaround time when requesting multiple tests on frozen samples, please submit separate frozen specimens for each test requested.

Storage Instructions:

Freeze; stable at room temperature for 24 hours. Stable refrigerated for 48 hours or frozen for three months. Freeze/thaw cycles: stable x1

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