South Karelia District of Social and Health Services, Lappeenranta, Finland Unit of General Practice, Oulu University Hospital, Oulu, Finland Institute of Health Sciences, University of Oulu, Oulu, Finland Health Centre of Oulu, Oulu, Finland Paediatric Research Centre, Tampere University Hospital and University of Tampere, Tampere, Finland Finnish Institute of Occupational Health, Oulu, Finland Department of Mathematical Sciences, University of Oulu, Oulu, Finland.
The cumulative incidence of parental-reported symptoms of food allergy (FA) during the first years of life is estimated to exceed 30%. However, the occurrence and determinants of FA testing in a general child population have remained unknown.
The study population comprised all 5920 children aged 0-4 yr in the province of South Karelia, Finland, identified from the nationwide population register. The study included a questionnaire survey and a retrospective collection of FA test results (skin prick tests, IgE antibodies, or open food challenges) from the patient records of the entire study population. The questionnaire and patient record data were linked together on an individual basis with the parents' permission.
A total of 5849 FA tests had been performed on 961 children. By the age of 4 yr, the cumulative incidence of FA testing was 18% for any food item; 17% for essential items (milk, egg, cereals) and 9% for other food items. Essential food items had been tested in 90% of children who reportedly had a physician-diagnosed FA for these. The incidence of testing was 30% higher in boys than in girls and twofold higher among the offspring whose either or both parents reportedly had some allergic manifestation.
A large proportion of children are subjected to FA testing in their early years. This result shows the need to evaluate the financial burden of FA testing and to improve current testing practices.
To examine whether the season of birth or season of the early phase of gestation is associated with sensitisation to food allergens in children, with special reference to mothers' pollen exposure in spring.
A population-based cohort study linking information from a questionnaire survey to allergy tests performed on the target population and regional pollen counts.
Children born in 2001-6 who were resident in the province of South Karelia, Finland, at the time of the survey (N=5920).
A positive result in any food allergy test or food-specific immunoglobulin E test (sIgE).
The cumulative incidence of a positive food allergy test up to the age of 4 years was highest among children born in October-November (10%) and lowest among those born in June-July (5%), and correspondingly highest among children who were in their 11th gestational week in April-May (11%), the season of high concentrations of birch and alder pollen, and lowest among those reaching that stage in December-January (6%). The amplitude of seasonal variation in any test, estimated as the relative ratio between the peak and trough of the smoothed incidence curve over the year, was 2.03 (95% CI 1.52 to 2.76). The amplitudes of positive sIgE were especially pronounced for milk (3.07; 95% CI 1.81 to 5.50) and egg (3.03; 95% CI 1.86 to 5.18).
Children having their early gestational period in the pollen season for broad-leafed trees are more prone to sensitisation to food allergens than other children.
Few epidemiological studies exist on food-associated symptoms and allergies in large unselected child populations.
To describe the design, methods and participation rate of the South Karelian Allergy Research Project (SKARP), a population-based epidemiological study on food-associated symptoms and physician-diagnosed food allergies.
The study population of 5,973 children born between 2001 and 2006 and resident in the province of South Karelia, Finland, was identified from the nationwide population register. The parents received a questionnaire to be returned at their child's annual visit to the child health clinic, where supplementary interviews were performed. Results of allergy tests (skin prick tests, immunoglobulin E antibodies and open food challenges) performed on participants and non-participants were collected from the relevant health care units in the area.
Participation rates in the questionnaire study were 54% (644/1,194) among the parents of neonates and 69% (3308/4,779) among those of the children aged 1 to 4 years. Cooperation with the child health clinics and mailing of a reminder questionnaire improved participation by 8 and 10 percentage points, respectively. The final participation rate seemed to be unaffected by whether the child had or had not been tested for suspected allergy.
A reasonably good participation rate and almost complete coverage of allergy tests were achieved thanks to successful cooperation with the child health clinics and test laboratories. This baseline study forms a representative database to estimate the occurrence of food-associated symptoms, physician-diagnosed food allergies and allergy testing in the general population.