Lower respiratory tract infections (LRTI) in patients with chronic lung diseases are a common acute reason to consult respiratory practitioners and often lead to inadequate prescription of antibiotics. The primary objective of the investigators study was to determine the diagnostic accuracy of point-of-care testing (POCT) for procalcitonin (PCT) in identifying pneumonia as a bacterial infection in outpatients with LRTI.

Lower respiratory tract infections (LRTI) are a common acute reason to consult general practitioners or lung specialists and most patients receive an antibiotic prescription. Despite the vast majority of LRTI are caused by viruses, the lack of clinical, radiological, and laboratory tests to safely rule out bacterial involvement in LRTI still drives antibiotic treatment today Procalcitonin (PCT) has been shown to be a useful biomarker for differentiating between viral and bacterial infections in the emergency department and is now available as a point-of-care testing (POCT). The primary objective of the investigators study was to determine the diagnostic accuracy of POCT PCT in identifying bacterial infection in outpatients with LRTI. All patients aged 18 years or older with signs and symptoms of an LRTI as the leading diagnosis of the respiratory physicians are eligible. The medical assistant measure PCT from venous or capillary whole blood using the portable commercially available BRAHMS PCT direct point-of-care test (Thermo-Fischer Scientific). The stepwise procedure involve pipetting 20µl of the sample into the test disc before loading this onto the analyzer and pressing run. This immunoassay provides a quantitative result in 20 minutes. In suspicion of pneumonia (positive auscultation finding or clinical noticed symptoms compatible with pneumonia) a chest x-ray will be done. Members of the study team conduct standardised phone interviews of all participants on day 28.

Inclusion Criteria:

• Age 18 years or older
• Clinical diagnosis of lower respiratory tract infection

Exclusion Criteria:

• Active malignancies
• Cystic fibrosis
• Solid organ or stem cell transplantation
• Chronic infection (endocarditis, osteomyelitis, active tuberculosis)
• Pregnancy