Utility of serum procalcitonin values in patients with acute exacerbations of chronic obstructive pulmonary disease: a cautionary note

Abstract

Background: Serum procalcitonin levels have been used as a biomarker of invasive bacterial infection and recently have been advocated to guide antibiotic therapy in patients with chronic obstructive pulmonary disease (COPD). However, rigorous studies correlating procalcitonin levels with microbiologic data are lacking. Acute exacerbations of COPD (AECOPD) have been linked to viral and bacterial infection as well as noninfectious causes. Therefore, we evaluated procalcitonin as a predictor of viral versus bacterial infection in patients hospitalized with AECOPD with and without evidence of pneumonia.

Methods: Adults hospitalized during the winter with symptoms consistent with AECOPD underwent extensive testing for viral, bacterial, and atypical pathogens. Serum procalcitonin levels were measured on day 1 (admission), day 2, and at one month. Clinical and laboratory features of subjects with viral and bacterial diagnoses were compared.

Results: In total, 224 subjects with COPD were admitted for 240 respiratory illnesses. Of these, 56 had pneumonia and 184 had AECOPD alone. A microbiologic diagnosis was made in 76 (56%) of 134 illnesses with reliable bacteriology (26 viral infection, 29 bacterial infection, and 21 mixed viral bacterial infection). Mean procalcitonin levels were significantly higher in patients with pneumonia compared with AECOPD. However, discrimination between viral and bacterial infection using a 0.25 ng/mL threshold for bacterial infection in patients with AECOPD was poor.

Conclusion: Procalcitonin is useful in COPD patients for alerting clinicians to invasive bacterial infections such as pneumonia but it does not distinguish bacterial from viral and noninfectious causes of AECOPD.

Keywords: bacterial infection; bronchitis; chronic obstructive pulmonary disease; procalcitonin; virus.

Figure 1

Flow chart of patient groups. Bacteriology is divided into reliable and not reliable. Abbreviations: V, viral alone; B, bacterial alone; BV, bacterial + viral; none, no microbiologic diagnosis; COPD, chronic obstructive pulmonary disease.

Figure 2

Receiver operator curve for procalcitonin as a diagnostic tool for bacterial infection in patients with a documented viral infection and acute exacerbations of chronic obstructive pulmonary disease without pneumonia. Specificity is indicated on y-axis and sensitivity on x-axis.

Figure 3

Procalcitonin values in subjects with acute exacerbations of chronic obstructive pulmonary disease without pneumonia. Individual procalcitonin values expressed as ng/mL on a log 10 scale. Viral alone patients are shown on admission (V1), day 2 (V2), and day 28 (V3) and bacterial + viral are shown on admission (BV1), day 2 (BV2), and day 28 (BV3) and bacterial alone on admission (B1), day 2 (B2), and day 28 (B3). The 0.25 ng/mL and 0.50 ng/mL procalcitonin levels are indicated by the dotted lines.