Hypereosinophilia: Biological investigations and etiologies in a French metropolitan university hospital, and proposed approach for diagnostic evaluation

Objectives We aimed to evaluate the usefulness of biological investigations in cases of eosinophilia in our area (French Alps). Methods We retrospectively included all adult patients attending the infectious disease and internal medicine units between 2009 and 2015 with eosinophilia ≥1 G/l. Results We identified 298 cases (129 women and 169 men). In 139 patients, eosinophilia had not been addressed. In the 159 others, the cause of eosinophilia was identified in 118 (74.2%). The main identified causes at the time were drug reactions (24.5%, mostly β-lactams and allopurinol), infectious diseases (17.0%), vasculitis (8.2%), autoimmune diseases (6.9%), and malignant diseases (6.2%). In patients with a skin rash, eosinophilia was significantly more often investigated, and a diagnosis significantly more often made. Helminthosis were mainly diagnosed in tropical travelers (18/24) excepting toxocariasis (3 non-travelers). Stool examination for helminthosis was positive in 5/76 patients (6.6%) (all tropical travelers); 391 helminth serologies were performed in 91 patients, with 7.9% being positive (all but 3 positive cases were travelers). Anti-neutrophil cytoplasmic antibodies (ANCA) were positive in 26/112 patients (23.2%), with 9 cases of vasculitis identified. Conclusions Drug-related eosinophilia is the main etiology. Search for helminthosis is not recommended among non-travelers (excepting toxocariasis). ANCA should be performed early so as not to overlook vasculitis.