Ability of procalcitonin to distinguish between bacterial and nonbacterial infection in severe acute exacerbation of chronic obstructive pulmonary syndrome in the ICU

BackgroundTo assess the ability of procalcitonin (PCT) to distinguish between bacterial and nonbacterial causes of patients with severe acute exacerbation of COPD (AECOPD) admitted to the ICU, we conducted a retrospective analysis of two prospective studies including 375 patients with severe AECOPD with suspected lower respiratory tract infections. PCT levels were sequentially assessed at the time of inclusion, 6 h after and at day 1, using a sensitive immunoassay. The patients were classified according to the presence of a documented bacterial infection (including bacterial and viral coinfection) (BAC+group), or the absence of a documented bacterial infection (i.e., a documented viral infection alone or absence of a documented pathogen) (BAC- group). The accuracy of PCT levels in predicting bacterial infection (BAC+group) vs no bacterial infection (BAC- group) at different time points was evaluated by receiver operating characteristic (ROC) analysis.ResultsRegarding the entire cohort (n=375), at any time, the PCT levels significantly differed between groups (Kruskal-Wallis test, p<0.001). A pairwise comparison showed that PCT levels were significantly higher in patients with bacterial infection (n=94) than in patients without documented pathogens (n=218) (p<0.001). No significant difference was observed between patients with bacterial and viral infection (n=63). For example, the median PCT-H-0 levels were 0.64 ng/ml [0.22-0.87] in the bacterial group vs 0.24 ng/ml [0.15-0.37] in the viral group and 0.16 ng/mL [0.11-0.22] in the group without documented pathogens. With a c-index of 0.64 (95% CI; 0.58-0.71) at H-0, 0.64 [95% CI 0.57-0.70] at H-6 and 0.63 (95% CI; 0.56-0.69) at H-24, PCT had a low accuracy for predicting bacterial infection (BAC+group).ConclusionDespite higher PCT levels in severe AECOPD caused by bacterial infection, PCT had a poor accuracy to distinguish between bacterial and nonbacterial infection. Procalcitonin might not be sufficient as a standalone marker for initiating antibiotic treatment in this setting.