Eosinophilia in sick neonates.

Eosinophilia is common in the neonatal period. However, its causes, pathomechanism and clinical significance are still unknown. Previous reports have described that eosinophilia may be associated with numerous conditions (establishment of an anabolic state, drug reactions, response to foreign antigens, chronic lung disease, erythropoietin treatment and infections). The aim of this study was to evaluate the possible association of various conditions, especially infection, with eosinophilia and to clarify whether recognition of increase in eosinophil count is of any clinical significance in the management of a sick neonate. Fifty-six neonates with eosinophilia (absolute eosinophil count > 700/mm3) and 55 control neonates matched for gestational age, birth weight and hospitalization days were included in the study. A significant difference between the two groups was found only in blood transfusions, immuno-globulin treatment, specific antibiotic treatment and infectious disease. However, neonates who develop sepsis and are treated with antibiotics and immuno-globulin are more often transfused. It can thus be concluded that the main relationship observed is between eosinophilia and infection whereas the other associations are secondary. The relative risk factor for infection when the absolute eosinophil count is > 700/mm3, is 1.58, with a confidence interval 1.30-1.91. Eosinophilia seems to be a reliable indicator of sepsis while normal absolute eosinophil count does not exclude infection. Infection should be strongly considered in the evaluation of a sick neonate with eosinophilia.