Procalcitonin (PCT; synonym: PCT test) is a precursor of calcitonin. It belongs to the acute-phase proteins and is formed in the C cells of the thyroid gland and neuroendocrine glands of various internal organs.The formation of procalcitonin is mainly influenced by bacterial infections. In viral diseases, there is a maximum slight increase, usually it remains normal.After the occurrence of bacterial, fungal and parasitic infection, it increases within a few hours (2-3 h) and reaches its maximum after 24 hours. Its biological half-life is 25-30 hours. A lack of decrease is evidence of persistence of infection!
The procedure
Material needed
- Blood serum
Preparation of the patient
- Not known
Disruptive factors
- Centrifuge blood sample, freeze serum.
Standard values
| Value in ng/ml | |
| Normal value | < 0,005 |
| Local inflammation and infection possible | < 0,5 |
| Moderate systemic infection | 0,5-2 |
| Severe systemic infection | 2-10 |
| Most severe systemic infection | > 10 |
1 ng/ml = 1 μg/l
Indications
- Suspicion of severe bacterial infection
- Suspicion of sepsis (blood poisoning)
- Therapy control of severe infections or sepsis (prognostic factor).
Interpretation
Interpretation of increased values
- Bacterial systemic infection (infection that spreads throughout the body).
- Persistent or severe cardiogenic shock
- Thyroid carcinoma (cancer of the thyroid gland)
- Use of the heart-lung machine
- Use of drugs that induce cytokines; these include interleukin-2 or anti-lymphocyte globulin
- Heat stroke
- Small cell bronchial carcinoma (lung cancer)
- Multi-organ failure
- Polytrauma – severely injured person in whom at least one injury or the combination of multiple injuries is life-threatening
- Newborn (< 48 hours after birth).
Bacterial infection of the lower respiratory tract.
| PCT value | Interpretation | Recommendation |
| < 0.1 μg/l | No bacterial infection of the lower respiratory tract. | No antibiotic therapy |
| 0.1-0.25 μg/l | Bacterial infection appears unlikely | Antibiotic therapy is not advised; depending on the clinical picture, a control examination should be performedNote: Note below on atypical bacteria. |
| 0.26-0.5 μg/l | Bacterial infection is likely | Antibiotic therapy is recommended |
| > 0.5 μg/l | Bacterial infection of the lower respiratory tract is very likely. | Immediate antibiotic therapy is indicated. |
| > 2.0 μg/l | Bacterial sepsis is present with increased probability |
1 μg/l = 1 ng/ml
Under antibiotic therapy and PCT < 0.25 μg/l: the antibiotic can be discontinued. Interpretation of lowered values
- Not relevant to disease
Further notes
- Not applicable in newborns up to the third day of life.
- In elderly patients, PCT is suitable for mapping the prognosis and severity of pneumonia.
- Bacterial bronchitis or pneumonia often show procalcitonin levels around 0.25-0.5 μg/l.
- Viral infections: < 0.5 μg/l – 2.0 μg/l; median: 0.09 ng/ml.
- Atypical bacteria (Chlamydia, Rickettsia, Mycoplasma, Legionella) as causative agents of pneumonia: median 0.2 ng/l !!!!
- Typical bacterial pneumonia: 2.5 ng/dl
- Note: Detection of elevated inflammatory levels such as C-reactive protein (CRP) or procalcitonin (PCT) alone should not be an indication for antibiotic therapy (German Society of Infectious Diseases).
