Trend of circulating eosinophils in healthy children and children suffering from infectious diseases. A retrospective study

INTRODUCTION: Acute bacterial and viral infections are accompanied by a marked diminution in circulating eosinophils in the blood. This forms part of the host's physiological response to acute infection and was first studied in adults early this century. The aims of this study were to check whether eosinopenia during acute phlogosis is a phenomenon present in pediatric patients, and whether the trend is comparable to the experimental models reported; to describe the trend of circulating eosinophils in the remission process. METHODS: A retrospective study was performed in 34 children hospitalised in the Pediatric Hospital of AUSL 2-Lucca (Italy) for bacterial or viral infective diseases documented by cell culture or presumed diagnosed. Children with the following characteristics were excluded from the study: 1) blood samples collected for hemochrome analysis at times other than normal (7-8 a.m.); 2) cortisone treatment administered up to 5 days prior to blood sample and/or during hospitalisation; 3) positive personal anamnesis for manifest allergic diseases. On admittance (children during acute phase) and at the start of remission, an absolute count of circulating eosinophils was performed in these children using an automatic globule counter. Sixty-six children with non evident infective and/or inflammatory diseases were included in the study as a control group. This group was also selected in the same way as infective subjects. RESULTS: The mean number of circulating eosinophils was 288 (+/- 248) in the control group, 46 (+/- 58) in subjects at the acute phase of infective pathology and 252 (+/- 162) in infective patient during the remission phase. The difference between the two means was statistically significant. This characteristic falling and rising trend of circulating eosinophils was found in 33 of the 34 infective subjects examined. CONCLUSIONS: Eosinophil values found in control subjects are broadly in line with those reported in the literature. Eosinopenia during the course of acute infection and the early rise during remission represent a characteristic phenomenon indicating the body's "normal" response to a non-parasitic infection. Both eosinophil levels, namely in the control group (288/mm3) and in acute-phase subjects (46/mm3), should be regarded as "normal" provided they refer to the appropriate situation. The precocity and precision with which the eosinophil trend follows the phases of the infection underlines the value of the assay of these cells as a reliable parameter for monitoring acute infection. There are also indications that, in an inflammatory situation, the behaviour of circulating eosinophils may provide a practical clinical marker of the predominant lymphocyte pattern (Th1 or Th2), as well as the phase of phlogosis, active or remission.