[Prediction of food allergy by using cord blood IgE levels]

As more attention is paid to food allergy which is already regarded as a public health problem, there is still a lot of uncertainty as to the mechanisms and there are limited therapeutic methods for this problem. It is of importance to screen the susceptible infants as early as possible. The present study was conducted to learn whether cord blood IgE levels (CBIgE) could be used as a predictor of food allergy, and to find out factors which influence the predictive accuracy of CBIgE.

The present study enrolled 118 infants born between April 2001and July 2001, and the authors followed up the infants until they were 4 months old. At the end of follow up, 105 infants had complete data for evaluation. Paper radioimmunosorbent tests (PRIST) were used for CBIgE assay, and parents were required to answer the standard questionnaires and the food skin prick tests (SPT) were taken for all infants.

At the end of follow-up, the infants were divided into 3 groups based on food allergy status: FA group with obvious food allergy, SFA group with suspected food allergy and NFA group without allergy. The median values of CBIgE levels in FA group were higher than those in SFA and NFA groups (4.80 IU/L, 0.55 IU/L, 0.87 IU/L, P < 0.01). When the cutoff value for CBIgE was set at 0.9 IU/L (CBIgE(0.9)), 42.9% of infants were found to have food allergy in the higher CBIgE group, 6.7% in the lower CBIgE group (P < 0.01, RR 95% CI = 2.715 approximately 15.221); when the cutoff value was set at 0.5 IU/L (CBIgE(0.5)), 30.9% in the higher CBIgE group and 5.00% in the lower CBIgE group (P < 0.01, RR 95% CI = 1.954 approximately 19.552). In addition, the sensitivity of CBIgE(0.9).as a predictor of food allergy, was 78.95% and the specificity, efficiency and odd product were 73.68%, 74.74%, and 10.50, generally better than CBIgE(0.5) of which the sensitivity, specificity, efficiency, odd product were 89.47%, 5.00%, 57.89%, 8.5 (P < 0.01). With the multi-factor stepwise regression analysis, our study indicated that exposure to cigarette smoke (OR 95%CI = 4.3340 approximately 71.2432), animal fur (OR 95% CI = 1.9869 approximately 30.7472), and egg supplement (OR 95% CI = 1.9340 approximately 25.8885) before 4 months of age might be the risk factors which may result in the predictive uncertainty of CBIgE.

Increased CBIgE levels might be the risk factor which result in food allergy; CBIgE(0.9), as a predictor of food allergy, is superior to CBIgE(0.5). However, some environmental factors, such as early exposure to cigarette smoke, animal fur and too early egg supplement would lead to predictive uncertainty of CBIgE.