Influence of atopic history on cord blood IgE.

To the Editor: An increase in cord blood IgE (CB-IgE) is considered an effective immunologic predictor which can be used to screen neonates for the risk of atopic diseases.1,2 Maternal atopic diseases and family atopic history have been proposed as two important risk factors determining CB-IgE in neonates.1,2,3 To determine the influence of atopic family history on cord blood IgE, a total of 201 cord blood samples were examined for total IgE concentration from 100 newborns with a family history of atopic disorders and 101 newborns with no history of atopic disorders, assigned as a control or low-risk group, from the Obstetric Ward at Hafez Hospital, Shiraz, Iran, from August to December 2002. All were ethnic Iranian families and informed consent was obtained from parents. This study was approved by our university ethics committee.

The atopic history of parents was collected in the third trimester by means of a standard questionnaire of asthma, allergic rhinitis, atopic dermatitis, and urticaria based on the ‘International Study of Asthma and Allergies in Childhood’ questionnaire.4 A last year medical student interviewed mothers and filled in the questionnaires.

The serum total IgE level of cord blood was determined by enzyme-linked immunosorbent assay (ELISA). A standard calibration curve was constructed. Elevated cord blood IgE values were cut off at the level of 0.5 IU/mL according to the previous reference cut off point.5 All data were processed using the SPSS program. There was no significant difference in mean age of mothers, mean gestational age, and mean birth weight between case and control groups. Fifty-one newborns in the case group and 65 newborns in the control group had values of cord blood IgE higher than 0.5 IU/mL (P=0.158, chi-square) (Figure 1). We found no significant difference for cord blood IgE levels between the case and control groups.

Figure 1

Distribution of cord blood IgE according to family atopic history.

Our study demonstrated that a family history of atopy is not a risk factor for elevated CB-IgE. The same result was achieved in a survey conducted in Taiwan, indicating that allergic history of parents does not correlate with elevated CB-IgE levels of neonates.6 However, another study conducted in the same region demonstrated that family history of atopy is a risk factor for elevated CB-IgE.7 In comparing the results of the present study with others one should consider the different methods for determination of IgE and different cut-off points used in the analysis, as well as differences in the population groups examined. Researchers have frequently argued about the bias from questionnaires of allergy history because the questionnaires were answered by mothers, who probably misinterpret the paternal allergic history.8 Certain studies have shown that a maternal history of atopy, but not paternal history correlates with the elevated CB-IgE levels, suggesting that maternal and/or placental factors can significantly affect prenatal IgE synthesis.1,9 In a study conducted in Germany the influence of atopic family history on CB-IgE proved to be strong and the percentage of elevated IgE values increased significantly with the number of atopic family members.3 Kaan et al found that a maternal history of asthma was the most important determinant for high CB-IgE,2 and Magnusson reported that infants with a positive immediate family history had a higher incidence of elevated cord IgE.1 We tried to define clear criteria so as to eliminate questionnaire bias. To avoid contamination at sampling cord blood was collected using direct needle aspiration of the cord vein.10 Also, acceptable techniques were used in detecting CB-IgE levels and therefore existing variations in results with some other reports should be a matter of ethnic variations. In conclusion, the influence of atopic history on cord blood IgE levels was not confirmed in this study.