Allergic outcomes
Data on parent-reported doctor diagnosis of asthma and allergic rhinitis
(AR) were collected at ages 0.5, 1, 1.5, 2, 4, 6, 10 and 15. If the time
between follow-ups was longer than one year (e.g., 10 to 15 years), the
presence of the diagnosis was asked separately for each year since the
previous follow-up (e.g., 10, 11, 12, 13, 14 and 15). In line with our
previous analyses, 17 only information collected from
age 3 onwards was used due to difficulty of accurate diagnosis of these
outcomes at younger ages. Asthma at ages Y = 3, 4, … 15 was
defined as a positive response to “Was your child diagnosed with asthma
by a doctor at the age of Y years?” AR at ages Y = 3, 4, … 15
was defined as a positive response to “Was your child diagnosed with
hay fever/allergic rhinitis by a doctor at the age of Y years?”
Specific immunoglobulin E (IgE) against common allergens was assessed at
ages 2, 6, 10 and 15 using the standardized CAP-RAST FEIA method
(ThermoFischer, Freiburg, Germany). At 2 years, allergic sensitization
was tested to tree and grass pollen (RX1), mold, cat and house dust
mites. At 6, 10 and 15 years, allergic sensitization was tested by using
inhalant mix SX1, which consists of house dust mite, cat, dog, mold,
birch, rye, mugwort and timothy grass allergens. Allergic sensitization
to aeroallergens was defined as IgE > 0.35 kU/L for at
least one of the tested inhalant allergens at 2 years and for the SX1
mix at the other timepoints. Allergic sensitization to food allergens
was defined as IgE > 0.35 kU/L for allergens in the FX5
screening test (milk, peanut, eggs, soya, cod and wheat flour) at all
timepoints.