Chest
Volume 138, Issue 5, November 2010, Pages 1108-1115
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Original Research
COPD
Procalcitonin vs C-Reactive Protein as Predictive Markers of Response to Antibiotic Therapy in Acute Exacerbations of COPD

https://doi.org/10.1378/chest.09-2927Get rights and content

Background

Rational prescription of antibiotics in acute exacerbations of COPD (AECOPD) requires predictive markers. We aimed to analyze whether markers of systemic inflammation can predict response to antibiotics in AECOPD.

Methods

We used data from 243 exacerbations out of 205 patients from a placebo-controlled trial on doxycycline in addition to systemic corticosteroids for AECOPD. Clinical and microbiologic response, serum C-reactive protein (CRP) level (cutoffs 5 and 50 mg/L), and serum procalcitonin level (PCT) (cutoffs 0.1 and 0.25 μg) were assessed.

Results

Potential bacterial pathogens were identified in the majority of exacerbations (58%). We found a modest positive correlation between PCT and CRP (r = 0.46, P < .001). The majority of patients (75%) had low PCT levels, with mostly elevated CRP levels. Although CRP levels were higher in the presence of bacteria (median, 33.0 mg/L [interquartile range, 9.75–88.25] vs 17 mg/L [interquartile range, 5.0–61.0] [P = .004]), PCT levels were similar. PCT and CRP performed similarly as markers of clinical success, and we found a clinical success rate of 90% in patients with CRP ≤ 5 mg/L. A significant effect of doxycycline was observed in patients with a PCT level < .1 μg/L (treatment effect, 18.4%; P = .003). A gradually increasing treatment effect of antibiotics (6%, 10%, and 18%), although not significant, was found for patients with CRP values of ≤ 5, 6–50, and > 50 mg/L, respectively.

Conclusions

Contrary to the current literature, this study suggests that patients with low PCT values do benefit from antibiotics. CRP might be a more valuable marker in these patients.

Section snippets

Materials and Methods

The methods, design, and outcomes of the above-mentioned trial have been described previously in detail.14 In short, 265 exacerbations from 223 patients were enrolled between August 2002 and February 2008 into a randomized placebo-controlled trial investigating the efficacy of doxycycline in addition to systemic corticosteroids for treatment of AECOPD. The study population consisted of patients ≥ 45 years of age, diagnosed with COPD (Global Initiative for Chronic Obstructive Lung Disease stages

Baseline Characteristics

In the original randomized trial, 265 exacerbations were enrolled. The per-protocol group of this trial, consisting of 258 patients, was used for the current study. Fifteen patients were excluded because no serum samples were stored, which made assessment of PCT levels impossible (Fig 1). We evaluated 243 exacerbations from 205 patients. Ninety-five were assigned to doxycycline and 110 to placebo. Table 1 shows the baseline characteristics, which are similar to the original trial.14 A potential

Discussion

To the best of our knowledge, the current study is the first to assess the value of PCT and CRP as markers of bacterial presence, clinical outcome, and efficacy of antibiotics and it has revealed four important new findings. First, we found only a moderate correlation between PCT and CRP in AECOPD. Importantly, most patients with a PCT level of < 0.1 μg/L had an elevated CRP value, in many cases (27%) even exceeding 50 mg/L. Second, we found that CRP was associated with bacterial presence,

Conclusions

In conclusion, CRP and PCT in AECOPD are only moderately correlated, and CRP is associated with airway bacterial presence, whereas PCT is not. Furthermore, although antibiotic therapy in patients with low PCT levels could be discouraged based on the literature, the current study suggests a benefit. This challenges the role of PCT as a predictive marker in AECOPD. Patients with a CRP of ≤ 5 mg/L have a favorable outcome regardless of antibiotic therapy, whereas patients with a CRP > 50 mg/L show

Acknowledgments

Author contributions: Dr Daniels: contributed to data collection, analysis and interpretation of the data, and manuscript preparation.

Ms Schoorl: contributed to data collection, analysis and interpretation of the data, and manuscript preparation.

Dr Snijders: contributed to data collection, analysis and interpretation of the data, and manuscript preparation.

Dr Knol: contributed to statistical analysis.

Dr Lutter: contributed to interpretation of the data and critical revision of the manuscript.

Dr

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  • Funding/Support: This study was supported by an unrestricted grant from GlaxoSmithKline (The Netherlands).

    Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (http://www.chestpubs.org/site/misc/reprints.xhtml).

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