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.