Early biomarkers of allergic disease in children

An 18-year follow-up of allergy development related to nasal metachromatic cell findings during infancy

BACKGROUND

The ability to predict the development of allergic diseases in infants is important. Predictive biomarkers are wanted to improve the risk evaluation in addition to known heredity of allergy. Biomarkers taken during infancy need to be evaluated through longitudinal studies into adulthood. The objective of this study was to analyse the occurrence of metachromatic cells in the nasal mucosa during infancy (MC(infancy)) and evaluate the cells as predictive biomarkers of allergy development.

METHODS

Previously, MC(infancy) occurrences were analysed in 64 infants with and without allergy heredity, and related to allergy development at 18 months and 6 years of age. In this third follow-up at 18 years of age, current allergy symptoms were analysed. MC(infancy) findings were related to the cumulative number of allergic subjects. The predictive values of MC(infancy) and known heredity were compared.

RESULTS

The cumulative number of subjects with allergy was 46, probable allergy 5, and no allergy 13. Detected MC(infancy) predicted allergy with high accuracy (31/33), but negative MC(infancy) findings did not exclude the risk (15/31). In the group of allergic subjects positive MC(infancy) were found in 31/46 (67%), positive heredity in 37/46 (80%) and one/both factors positive in 43/46 (93%). Detection of MC(infancy) could precede the debut of allergy symptoms by many years.

CONCLUSIONS

Detected MC(infancy) predicted allergy development, but absence of MC(infancy) did not exclude the risk, and therefore this biomarker was not found to be adequate. There is a further need to find biomarkers with high ability to both predict and exclude the risk.

Do levels of immunoglobulin G antibodies to foods predict the development of immunoglobulin E antibodies to cat, dog and/or mite?

BACKGROUND

In children at high risk of inhalation allergy, food sensitization is associated with an increased risk for sensitization to inhalant allergens. Furthermore, this association was also found in a cross-sectional study.

OBJECTIVE

To examine in a prospective study, whether levels of IgG to foods (i.e. mixture of wheat and rice, mixture of soy bean and peanut, egg white, cow's milk, meat, orange and potato) indicate an increased risk for the future development of IgE antibodies to inhalant allergens in a low-risk population and whether they can be used as predictors of the subsequent development of IgE antibodies in young, initially IgE-negative children.

METHODS

Coughing children, aged 1-5, visiting their GPs, were tested for IgE antibodies to mite, dog and cat (RAST) and IgG (ELISA) to foods. All IgE-negative children were retested for IgE antibodies after two years. The IgG results (66 percentiles) of the first blood sample were compared to the RAST-scores of the second blood sample.

RESULTS

After two years, 51 out of 397 (12.8%) originally IgE-negative children, had become IgE-positive for cat, dog and/or mite. An increased IgG antibody level to wheat-rice (OR = 2.2) and to orange (OR = 2.0) indicated an increased risk of developing IgE to cat, dog or mite allergens. In addition to IgG to a mixture of wheat-rice and orange; total IgE, breastfeeding, eczema as a baby and age were the most important predictors for the subsequent development of IgE to inhalant allergens.

DISCUSSION

An increased IgG antibody level to a mixture of wheat-rice or orange, indicates an increased risk of developing IgE to cat, dog or mite allergens. This indicates that excessive activity of the mucosal immune system is present before IgE antibodies to airborne allergens can be demonstrated. Nevertheless, IgG to foods is not very helpful (with a positive predictive value of 16.5%, and negative predictive value of 90.6%) in identifying individual children at risk in clinical practice. However, besides other risk factors, IgG to wheat-rice and to orange could be useful as a screening test for studies in the early identification, i.e. before IgE antibodies can be detected, of children with an increased risk of developing IgE antibodies in the future.