Research on pathophysiology and the establishment of serum biomarkers for cigarette-smoke-associated acute eosinophilic pneumonia

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The presentation of acute eosinophilic pneumonia (AEP) closely resembles that of acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) including its idiopathic form, acute interstitial pneumonia (AIP). AEP usually lacks peripheral eosinophilia at the acute phase; therefore, the establishment of serum biomarkers for AEP would be clinically useful. We measured the levels of thymus-and activation-regulated chemokine (TARC/CCL17), eotaxin/CCL11, KL-6 and surfactant protein-D (SP-D) in serum for patients with acute parenchymal lung diseases including AEP (n=17), AIP (n=13), pneumonia-associated ALI/ARDS (n=12), and alveolar hemorrhage (n=7). To evaluate the diagnostic ability of each marker was estimated by measuring the area under the receiver operating characteristic curve (AUC). The serum TARC/CCL17 levels of AEP patients were much higher than those of patients in other disease groups. More importantly, high circulating TARC/CCL17 levels were observed in AEP even at acute phase when peripheral eosinophilia was absent. TARC/CCL17 showed the largest AUC, and the TARC/CCL17 levels with cut-off points between 6,259 and 7,039pg/ml discriminated AEP from other syndromes with sensitivity and specificity of 100%. The KL-6 level was low in most patients with AEP, and the sensitivity was 81.6% in cutoff with 100% specificity. The AUC for eotaxin/CCL11 and SP-D was small with the values of 0.73 (95% confidence interval [CI], 0.60 to 0.85) and 0.53 (95% CI, 0.31 to 0.64), respectively. This study indicates that the measurement of circulating TARC/CCL17 and KL-6 is useful for discriminating AEP from other causes of acute lung injury.