Procalcitonin levels in acute exacerbation of COPD admitted in ICU: a prospective cohort study

Background: Antibiotics are recommended for severe acute exacerbation of chronic obstructive pulmonary disease (AECOPD) admitted to intensive care units (ICU). Serum procalcitonin (PCT) could be a useful tool for selecting patients with a lower probability of developing bacterial infection, but its measurement has not been investigated in this population. Methods: We conducted a single center prospective cohort study in consecutive COPD patients admitted to the ICU for AECOPD between September 2005 and September 2006. Sputum samples or tracheal aspirates were tested for the presence of bacteria and viruses. PCT levels were measured at the time of admittance, six hours, and 24 hours using a sensitive immunoassay. Results: Thirty nine AECOPD patients were included, 31 of which (79%) required a ventilator support at admission. The median [25%-75% interquartile range] PCT level, assessed in 35/39 patients, was: 0.096 mu g/ L [IQR, 0.065 to 0.178] at the time of admission, 0.113 mu g/L [IQR, 0.074 to 0.548] at six hours, and 0.137 mu g/L [IQR, 0.088 to 0.252] at 24 hours. The highest PCT (PCTmax) levels were less than 0.1 mu g/L in 14/ 35 (40%) patients and more than 0.25 mu g/L in 10/ 35 (29%) patients, suggesting low and high probability of bacterial infection, respectively. Five species of bacteria and nine species of viruses were detected in 12/ 39 (31%) patients. Among the four patients positive for Pseudomonas aeruginosa, one had a PCTmax less than 0.25 mu g/L and three had a PCTmax less than 0.1 mu g/L. The one patient positive for Haemophilus influenzae had a PCTmax more than 0.25 mu g/ L. The presence or absence of viruses did not influence PCT at time of admission (0.068 vs 0.098 mu g/L respectively, P = 0.80). Conclusion: The likelihood of bacterial infection is low among COPD patients admitted to ICU for AECOPD (40% with PCT < 0.1 mu g/L) suggesting a possible inappropriate use of antibiotics. Further studies are necessary to assess the impact of a procalcitonin-based therapeutic strategy in critically ill COPD patients.