Clinical implications of initial peripheral eosinophilia in acute eosinophilic pneumonia

The initial peripheral eosinophil count (PEC) is rarely elevated but tends to increase during the clinical course of acute eosinophilic pneumonia (AEP). We evaluated whether initial peripheral eosinophilia is an indicator of mild disease in patients with AEP.

We retrospectively examined associations between initial peripheral absolute eosinophil count, inflammatory markers and clinical characteristics in 85 patients with AEP.

Of 85 patients, 24 (28%) had initial peripheral eosinophilia (>500/μL). Initial peripheral absolute eosinophil count was inversely correlated to white blood cell (WBC) count (ρ = -0.386, P < 0.001), neutrophil percentage (ρ = -0.645, P < 0.001) and C-reactive protein (CRP; ρ = -0.495, P < 0.001). During treatment, peripheral absolute eosinophil counts increased, while inflammatory markers (WBC, neutrophil percentage, and CRP) decreased. Patients with initial peripheral eosinophilia had a longer duration from onset of symptoms to admission (P = 0.006), had lower WBC counts, neutrophil percentages and CRP values (all P < 0.001), and higher oxygen saturation (P = 0.004) than patients with normal peripheral eosinophil counts. Oxygen requirements (P = 0.013), duration of oxygen administration (P = 0.028) and intensive care unit admission rates (P = 0.003) were lower in patients with initial peripheral eosinophilia. All patients survived and recovered fully after corticosteroid or conservative treatment.

Initial PEC may be related to a milder disease status on admission, compared with normal PEC in patients with AEP. This may help to stratify disease severity in AEP.