Increased eosinophil cation protein level in sensitized nonasthmatics is linked to subsequent hyperresponsiveness to methacholine. The Odense Schoolchild Study.

BACKGROUND

Increased levels of eosinophil cation protein (ECP) in sensitized subjects may reflect early stages of an ongoing inflammatory process and therefore precede asthma and bronchial hyperreactivity.

AIM

To study whether nonasthmatic subjects with sensitization to allergens and increased ECP levels are at a higher risk for subsequent increased bronchial reactivity compared with sensitized nonasthmatics with normal ECP levels.

METHODS

A prospective study of 240 schoolchildren with a mean age of 13.9 years (range: 12.6-15.9) who were followed up after 6.3 years. Bronchial reactivity was assessed by methacholine provocation testing. Sensitization was defined by one or more positive reactions (>3 mm wheal) to 10 common aeroallergens by skin prick testing. Increased ECP was defined as values above 20 microg/l. This separated the subjects into four categories: group 1: healthy controls without sensitization (n = 147); group 2: sensitized subjects with a serum ECP below 20 microg/l (n = 55); group 3: sensitized subjects with an ECP level at or above 20 microg/l (n = 16), and group 4: all asthmatics (n = 22).

RESULTS

Bronchial reactivity was similar in subjects of groups 2 and 3 at baseline (p = 0.8). Six years later, subjects from group 3 were more responsive to methacholine compared with subjects from group 2 (median: 12.7 versus 20.5 micromol; p < 0.05). In a logistic regression with hyperresponsiveness to methacholine at follow-up as dependent variable, the odds ratios (OR) for the groups were, with group 1 as reference: group 2: OR = 2.2 (0.8-6.6: p = 0.2), group 3: 5.9 (1. 6-21.7: p < 0.01).

CONCLUSION

Subjects with sensitization and increased ECP levels are subsequently more airway-responsive to methacholine compared with sensitized subjects with normal ECP levels. This supports the hypothesis that sensitization is linked to increased bronchial reactivity through a process in which markers of inflammation are involved.