Procalcitonin sensitivity - a test for the control of antibiosis in diseases of the respiratory tract

Procalcitonin synthesis is increased in all body cells during generalised bacterial infections. Along with CRP, it has proven its worth as an inflammation marker, to date mainly for monitoring high-risk patients with severe bacterial infections, sepsis and septic shock in intensive care. Here, persistently high and/or increasing procalcitonin values over the course of the disease are to be regarded as solid evidence of a poor prognosis.

In locally limited, bacterial and especially viral infections, however, only slight to moderate procalcitonin increases have been observed.

The introduction of the sensitive procalcitonin test has opened up new possibilities for making use of procalcitonin, including at family practices, for the differential diagnosis of unclear inflammatory and feverish illnesses, e.g. diseases of the lower respiratory tract (acute bronchitis, pharyngitis, exacerbation of chronic bronchitis and community-acquired pneumonia). Up to 80 % of these diseases are self-limiting viral infections in which antibiotics are ineffective and therefore unnecessary. By contrast, 75 % of all antibiotics prescribed in out-patient clinics are for the treatment of respiratory tract infections.

On the basis of the procalcitonin level as an objective criterion, a decision can quickly be made whether antibiotic therapy is necessary or whether a symptomatic treatment is sufficient.

Due to the fact that it drops rapidly when therapy is successful, procalcitonin can also be used as a decision criterion for determining the duration of antibiotic treatment.

Through procalcitonin-based monitoring of the antibiotic therapy (determining PCT after 3, 5 and 7 days), the consumption of antibiotics can be reduced significantly without compromising treatment success (Schuetz et al. BMC Health Serv. Res. 2007; 7,102). Besides reducing antibiotic-related adverse reactions, this also serves to reduce therapy costs and safeguard the pharmaceutical budget, and it also has positive effects on the development of resistance to antibiotics.

The following procalcitonin-values are proposed as a basis for making decisions:

PCT < 0.1 ng/ml No bacterial infection / no antibiosis
PCT > 0.1 to < 0.25 ng/ml Bacterial infection unlikely / no antibiosis
PCT > 0.25 to < 0.5 ng/ml Bacterial infection possible / antibiotic therapy is recommended
PCT > 0.5 ng/ml Suspected bacterial infection / antibiosis necessary
PCT > 2.0 ng/ml Serious bacterial infection / antibiosis obligatory
PCT > 10 ng/ml Severe bacterial sepsis or septic shock / antibiosis is a matter of life and death

Quantity and material
1 ml of serum (alternatively, EDTA plasma)

Interference factors
Haemolysis, lipaemia

Reference ranges
See table

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