Original article
C-reactive protein — can it be used as a marker of infection in patients with exacerbation of chronic obstructive pulmonary disease?

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Abstract

Background

Far from all patients with exacerbation of chronic obstructive pulmonary disease (COPD) benefit from antibiotic treatment. However, as these patients are often colonized with bacteria, even in a stable phase, there is no reliable method for establishing whether the patients have a significant bacterial infection and would benefit from antibiotic treatment. C-reactive protein (CRP) has proven to be useful as a marker of bacterial infection. The aim of this study was to assess to what degree CRP is elevated in patients with exacerbation of COPD.

Methods

A total of 166 consecutive patients admitted to a department of internal medicine at a university hospital in Copenhagen due to exacerbation of COPD were prospectively included in the study. Patients were asked whether they had experienced increased sputum purulence and whether they were on steroid treatment or not. Blood was drawn for determination of white blood cell count and CRP, and a chest X-ray was taken. Patients whose X-rays of the thorax showed changes compatible with pneumonia were considered to have pneumonia of bacterial origin.

Results

Pneumonia was diagnosed in 51 patients. Their median CRP was 97 mg/l (49–145 interquartile range). Among patients without pneumonia, 46% (51 / 115) had normal CRP values (0–10 mg/l); 64 had no increased sputum purulence and a median CRP of 8 mg/l (2.9–16 mg/l), which is significantly lower than in the 51 patients who reported increased sputum purulence and had a CRP of 45 mg/l (8.5–86 mg/l; p < 0.001).

Conclusion

CRP values are normal in nearly 50% of patients admitted due to exacerbation of COPD. In patients who have increased sputum purulence, the pattern of increase in CRP is similar to that seen in patients with pneumonia. This suggests that CRP may be used as a marker of significant bacterial infection. Thus, it may be used when deciding whether or not to start antibiotic treatment. This should be tested in a controlled trial.

Introduction

Exacerbation of chronic obstructive pulmonary disease (COPD) is a very common cause of hospital admission and is often associated with signs of infection, such as increased sputum volume or increased purulence of the sputum. In general, patients with exacerbation of COPD are advised to start antibiotic treatment [1], [2].

A possible disadvantage of the widespread use of antibiotics is the risk of emerging bacterial resistance. In a recent study, it was shown that the use of antibiotics, i.e., penicillin or cephalosporins, in children is associated with an increased prevalence of penicillin-resistant pneumococci [3]. Although, to our knowledge, no such study has been undertaken in patients with COPD, it may well be that widespread use of antibiotics in this group of patients is also associated with an increased prevalence of bacterial resistance. If so, more restrictive use of antibiotics may be warranted in COPD patients.

With regard to the use of antibiotics in exacerbations of COPD, the landmark study was performed 18 years ago by Anthonissen et al. [4]. In a randomized trial, it was shown that patients who fulfilled the criteria of increased breathlessness, increased sputum volume, and increased sputum purulence benefited from antibiotic treatment.

In recent years, C-reactive protein (CRP) has been introduced as a marker of bacterial infection. In a recent study undertaken among patients with exacerbations of COPD, CRP was reported to be more elevated in patients with increased sputum purulence than in those without [5]. This suggests that CRP may be considered when deciding whether or not to treat these patients with antibiotics.

The aim of the present study was to classify the exacerbations of a consecutive series of patients with exacerbation of COPD admitted to a department of internal medicine according to the Anthonissen criteria as well as to whether or not they reported increased sputum purulence. This information was related to biochemical markers of infection and to pre-hospital use of systemic steroids. Patients with exacerbations of COPD with and without pneumonia, as demonstrated by chest X-ray, were compared.

Section snippets

Material and methods

The study was conducted at Herlev University Hospital, which serves as a general district hospital for approximately 200,000 inhabitants in the county of Copenhagen. Patients admitted with exacerbations of COPD are randomly admitted to, and treated in, one of two wards. The patients included in this study were all admitted to the Department of Endocrinology throughout the year 1999.

On admission the patients were asked if they had experienced any of the three symptoms that constitute

Results

Pneumonia was diagnosed in 51 patients, based on changes in X-rays of the thorax; 115 patients showed no changes compatible with pneumonia on chest X-ray. There were no differences with regard to WBC count between patients with and without pneumonia. Moreover, there were no differences in the WBC count when those without pneumonia were grouped according to the number of positive Anthonissen criteria (Table 1). In patients without pneumonia, 46% (51 / 115) had normal CRP values. CRP was

Discussion

The present study shows that patients admitted to the hospital with exacerbation of COPD present with a large variation in CRP values, including a substantial number with normal values. However, patients who reported increased sputum purulence at admission had higher CRP values than those without increased sputum purulence. To some extent, the CRP values of patients with increased sputum purulence overlapped the values of those with pneumonia, as established by chest X-ray.

It has proved very

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