Eosinophilic inflammation of the airways is correlated with the severity of asthma. These cells are likely to play a part in the epithelial damage seen in this disease.

In unstable coronary artery disease, elevated levels of troponin T and C-reactive protein are strongly related to the long-term risk of death from cardiac causes. These markers are independent risk factors, and their effects are additive with respect to each other and other clinical indicators of risk.

The heterogeneity of the biologic response of COPD exacerbations can be defined. Sputum IL-1β, serum CXCL10, and peripheral eosinophils are biomarkers of bacteria-, virus-, or eosinophil-associated exacerbations of COPD. Whether phenotype-specific biomarkers can be applied to direct therapy warrants further investigation.

Rationale: Exacerbations of chronic obstructive pulmonary disease (COPD) and responses to treatment are heterogeneous. Objectives: Investigate the usefulness of blood eosinophils to direct corticosteroid therapy during exacerbations. Methods: Subjects with COPD exacerbations were entered into a randomized biomarker-directed double-blind corticosteroid versus standard therapy study. Subjects in the standard arm received prednisolone for 2 weeks, whereas in the biomarker-directed arm, prednisolone or matching placebo was given according to the blood eosinophil count biomarker. Both study groups received antibiotics. Blood eosinophils were measured in the biomarker-directed and standard therapy arms to define biomarker-positive and -negative exacerbations (blood eosinophil count . and < 2%, respectively). The primary outcome was to determine noninferiority in health status using the chronic respiratory questionnaire (CRQ) and in the proportion of exacerbations associated with a treatment failure between subjects allocated to the biomarker-directed and standard therapy arms. Measurements and Main Results: There were 86 and 80 exacerbations in the biomarker-directed and standard treatment groups, respectively. In the biomarker-directed group, 49% of the exacerbations were not treated with prednisolone. CRQ improvement after treatment in the standard and biomarker-directed therapy groups was similar (0.8 vs. 1.1; mean difference, 0.3; 95% confidence interval, 0.0-0.6; P ¼ 0.05). There was a greater improvement in CRQ in biomarker-negative exacerbations given placebo compared with those given prednisolone (mean difference, 0.45; 95% confidence interval, 0.01-0.90; P ¼ 0.04). In biomarker-negative exacerbations, treatment failures occurred in 15% given prednisolone and 2% of those given placebo (P ¼ 0.04). Conclusions: The peripheral blood eosinophil count is a promising biomarker to direct corticosteroid therapy during COPD exacerbations, but larger studies are required. Clinical trial registered with www.controlled-trials.com (ISRCTN 92422949).Keywords: chronic obstructive pulmonary disease; exacerbations; prednisolone; infection; eosinophils Acute exacerbations of chronic obstructive pulmonary disease (COPD) are associated with substantial morbidity and mortality (1, 2) and are heterogeneous with respect to inflammation (3, 4) and etiology (5-7). Although primarily associated with asthma, eosinophilic airway inflammation is present in some patients with COPD (8). Previous studies have shown that a sputum eosinophilia is associated with a positive response to corticosteroid treatment in stable COPD (9-11), and the sputum eosinophil count can be used to titrate corticosteroid therapy to reduce exacerbations of COPD (12).Current guidelines advocate the use of systemic corticosteroids during acute exacerbations of COPD because of improvements in the rate of recovery (13,14); this is despite being associated with significant side effects (15) and with limited benefits in reducing mortality (14). Increased eosinophilic air...

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