Point-of-care procalcitonin testing for lower respiratory tract infection in pulmonary outpatient care has limited value.

Lower respiratory tract infections (LRTI) are frequently the reasons for patients to visit their general practitioners or lung specialists; however, physicians tend to prescribe antibiotics less frequently than necessary. A readily available biomarker could help distinguish between viral and bacterial cause of LRTI. The primary objective of our study was to determine the diagnostic accuracy of point-of-care testing (POCT) of procalcitonin (PCT) in identifying bacterial pneumonia in outpatients with LRTI. All patients aged 18 years or older with signs and symptoms of LRTI who visited a respiratory physician were included in the study and their PCT levels were measured. In 110 patients enrolled in the study, three patients (2.7%) had PCT values above the threshold of 0.25 µg/L without proven bacterial infection, in contrast to seven patients with typical radiological signs of pneumonia without elevated POCT PCT levels. The AUC for PCT for the detection of pneumonia was 0.56 (p=0.685). POCT PCT showed limited specificity and sensitivity in distinguishing pneumonia from bronchitis or exacerbation of chronic respiratory diseases. PCT is a marker of severe bacterial infections and not suitable for milder infections in outpatient care.