A Retrospective Analysis of Patients Presenting with Eosinophilia and Strongyloidiasis

Rationale: Peripheral eosinophilia is a common finding among patients referred to hematology and immunology ambulatory care centers and may be linked to primary (i.e. clonal or idiopathic) or reactive conditions such as infections (especially helminths), neoplasms, connective tissue disorders, endocrinopathies, and allergies. We recently identified a cohort of patients diagnosed with strongyloidiasis, a disease caused by parasitic roundworms, in our urban population. Through this study, seek to identify the clinical variables that may be linked to baseline peripheral eosinophilia among these individuals.

Methods: We analyzed a retrospective cohort of 49 patients who had a positive Strongyloides stercoralis serology, and were seen between 2011 and 2014 at the Allergy/Immunology outpatient clinics of Montefiore Medical Center, Jacobi Medical Center, and North Central Bronx Hospital. We included adult patients who had data available regarding age, birthplace, and baseline serum total immunoglobulin E (IgE), absolute eosinophil counts (AEC), and serum 25-hydroxyvitamin D levels. We considered peripheral eosinophilia as greater than or equal to 500 cells per microliter, and patients were categorized as having eosinophilia or non-eosinophilia (i.e. less than 500 cells/microliter). We sought to further characterize the eosinophilic vs non-eosinophilic groups, and therefore calculated the mean age, baseline serum total IgE levels, and serum 25-hydroxyvitamin D levels in each group. We noted each patient's birthplace (Asia, Africa, Central/South America, Europe, United States, Caribbean), and determined the mean AEC for each birth location. In the eosinophilia versus non-eosinophilia groups, we determined the mean AEC change (baseline to post-treatment follow-up) in patients that received ivermectin treatment for strongyloidiasis. We utilized the two-sample t-test to compare numeric variables between the eosinophilia and non-eosinophilia groups, and recognized a p-value of less than 0.05 as statistically significant. Institutional Review Board approval was obtained from the Montefiore Medical Center, Bronx, New York.

Results: The cohort included 37 female and 12 male patients with an overall mean (SD) age of 55.8 (16.2) years. There were 37 'non-eosinophilia' patients with a mean AEC of 214.6 cells/microliter and 12 'eosinophilia' patients with a mean AEC of 993.3 cells/microliter. Patients born in the Caribbean Islands and Asia had the highest AEC, with means of 607.5 and 497.2 cells/microliter, respectively, of the eosinophilia sample. Patients in the 'non-eosinophilia' group had a mean age of 51.9 (15.4) years, while patients in the 'eosinophilia' group had a mean age of 67.5 (13.2) years (p=0.003). Baseline serum total IgE titers were significantly elevated in 'eosinophilia' patients with a mean of 1576.83 kU/L when compared to 'non-eosinophilia' patients with a mean of 285.1 kU/L, p=0.007. Serum 25-hydroxyvitamin D levels did not vary significantly between both groups (p=0.443). Of the patients that received a 2-day course of oral ivermectin (200 mcg/kg/day), the 'non-eosinophilia' patients had an increase in peripheral eosinophil counts following treatment with a mean AEC change of 180.8 cells/microliter when compared to 'eosinophilia' patients who had a decrease in eosinophil counts following treatment with a mean AEC change of 654.4 cells/microliter (p=0.003).

Conclusion: We identified several clinical characteristics that are associated with peripheral eosinophilia as a presenting feature in this cohort of patients diagnosed with strongyloidiasis. Importantly, most of the patients did not present with eosinophilia. Patients born in the Caribbean Islands and Asia presented with higher AEC; additional studies should be conducted in these individuals to determine genetic and environmental features that determine eosinophilia in the setting of strongyloidiasis. Older patients presented with higher eosinophil counts, and additional studies are needed to identify the contributing reasons. Patients in the 'eosinophilia' group saw a decrease in AEC following ivermectin treatment. Further studies should be conducted to determine if peripheral eosinophilia in patients can predict response to medication, and help optimize treatment plans.