medwireNews: Patients with community-acquired pneumonia (CAP) on a background of chronic obstructive pulmonary disease (COPD) have a different early inflammatory pattern than patients with CAP only, a prospective study shows.
The observed differences in the levels of certain cytokines could not be fully attributed to corticosteroid use in COPD patients.
"We showed that, on the first day of hospitalization, the systemic response to bacterial infection (not completely corticosteroid mediated) in patients with COPD is lower, especially in terms of levels of TNF [tumor necrosis factor]-α, IL[interleukin]-1, and IL-6 cytokines," report lead researcher Antoni Torres (Hospital Clinic, Barcelona, Spain) and colleagues.
Clinical, microbiologic, and immunologic data were collected from 367 patients on admission to a hospital with CAP plus COPD (n=117) or CAP only (n=250). The use of inhaled and oral corticosteroids was recorded, and pneumonia severity scores were calculated on the Pneumonia Severity Index (PSI) and CURB-65 (confusion, urea plasma level, respiratory rate, blood pressure, age over 65) scale.
On the first day of hospitalization, the researchers found that patients with CAP plus COPD had significantly lower serum levels of TNF-α, IL-1, and IL-6 compared with the CAP-only group. There was no difference in the levels of C-reactive protein, procalcitonin, IL-8, and IL-10.
When COPD patients using corticosteroids were excluded from the analysis, the decrease in IL-6 lost its significance.
Streptococcus pneumoniae was found to be the most frequent pathogen in both groups; however, patients with COPD and CAP were more likely to have a microbiologic diagnosis of Pseudomonas aeruginosa then patients with CAP only. This was no longer the case when COPD patients using corticosteroids were discounted.
Clinical severity and prognosis, as measured by mortality at hospitalization and at 30 and 90 days, were similar between the CAP-only and CAP plus COPD groups. This was despite patients with CAP and COPD scoring higher on the PSI and CURB-65 than patients with CAP only.
These results lead the authors to suggest that, in patients with CAP and COPD, the PSI and CURB-65 may not be good markers of CAP severity, and that "the low levels of circulating inflammatory biomarkers may have a nondetrimental effect on the hospital course and prognosis of these patients."
However, writing in Chest, the authors caution: "Our study is not intended or statistically powered to evaluate the clinical and prognostic effects of a different, early inflammatory response between patients with CAP only and those with CAP + COPD."
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