CRP levels distinguish pneumonia in COPD
By Kirsty Oswald, medwireNews Reporter
23 July 2013
Chest 2013; Advance online publication

medwireNews: Researchers have found that pneumonia results in a distinct inflammatory pattern to that of an acute exacerbation (AE) in chronic obstructive pulmonary disease (COPD).

In particular, an early peak in C-reactive protein (CRP) levels independently predicts pneumonia, which the team says could help physicians to exclude or confirm the condition when X-ray findings are in doubt.

The study involved 249 hospitalized COPD patients, of whom 133 were considered to have AECOPD and 116 community acquired pneumonia (CAP)-COPD.

The research team, led by Antoni Torres (University of Barcelona, Spain), found that patients with pneumonia had significantly higher biologic signaling in the first 3 days after admission compared with AECOPD patients; levels of CRP, procalcitonin, tumor necrosis factor alpha, and interleukins 1, 6, and 8 were all significantly greater.

CRP on day 1 independently predicted pneumonia, with patients in the fourth quartile having a 10.6-fold greater odds of the condition than those in the first quartile (≥20.5 vs ≤3.5 mg/dL). And, area under the curve analysis showed that at an optimum cut-off of 12.9 mg/dL, CRP discriminated between the two conditions with a sensitivity of 62%, a specificity of 63%, and an accuracy of 71%.

Additionally, the authors confirmed that the presence of chills, pleuritic pain, or sputum purulence were also independently predictive for CAP.

The authors also found other differences between CAP-COPD and AECOPD patients. Of note, AECOPD patients had greater severity of disease by lung function than CAP-COPD patients and, while this did not translate into poorer long- or short-term outcomes, they had a significantly higher readmission rate, at 24% versus 12%.

“This is a major issue in terms of health care cost,” comment the authors who say that studies identifying risk factors for short-term readmission are needed in both populations.

The team also reports a predominance of Haemophilus influenzae among AECOPD patients, while Streptococcus pneumoniae was more commonly detected in CAP-COPD patients.

Torres and colleagues suggest that CRP could be used as a diagnostic marker when chest X-ray findings are inconclusive in COPD patients. This could avoid the need for computed tomography, as well as the prescription of unnecessary antibiotics, they say, adding that CRP could also pick up new infiltrates that X-ray is insufficiently sensitive to detect.

“We think that quick and easy detection of CRP may be useful in some cases (e.g. doubtful infiltrates, condensation in emphysema patients) with the possibility of screening for new pulmonary infiltrate,” they conclude.

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